I am using gnome-calendar (3.36.2) on Linux Mint 20 (Ulyana), Cinnamon 4.6.7.
I am able to replicate the crash by opening gnome-calendar, then clicking on "Manage your calendars" and toggling / untoggling different calendars at random.
Here's a log from journalctl if it's of use:
-- The job identifier is 27260.
Feb 08 01:44:15 saturn org.gnome.Calendar[249540]: **
Feb 08 01:44:15 saturn org.gnome.Calendar[249540]: GcalTimeline:ERROR:../src/core/gcal-timeline.c:212:increase_completed_calendars: assertion failed: (self->completed_calendars <= g_hash_table_size (self->calendars))
Feb 08 01:44:15 saturn org.gnome.Calendar[249540]: Bail out! GcalTimeline:ERROR:../src/core/gcal-timeline.c:212:increase_completed_calendars: assertion failed: (self->completed_calendars <= g_hash_table_size (self->calendars))
Feb 08 01:44:15 saturn systemd[1]: Started Process Core Dump (PID 249641/UID 0).
-- Subject: A start job for unit systemd-coredump@41-249641-0.service has finished successfully
-- Defined-By: systemd
-- Support: http://www.ubuntu.com/support
--
-- A start job for unit systemd-coredump@41-249641-0.service has finished successfully.
--
-- The job identifier is 27350.
Feb 08 01:44:16 saturn systemd-coredump[249642]: Process 249540 (gnome-calendar) of user 1000 dumped core.
Stack trace of thread 249540:
#0 0x00007f1ff002018b __GI_raise (libc.so.6 + 0x4618b)
#1 0x00007f1feffff859 __GI_abort (libc.so.6 + 0x25859)
#2 0x00007f1ff0523b43 n/a (libglib-2.0.so.0 + 0x1db43)
#3 0x00007f1ff0580b2f g_assertion_message_expr (libglib-2.0.so.0 + 0x7ab2f)
#4 0x00005562ad7685a7 n/a (gnome-calendar + 0x455a7)
#5 0x00007f1ff0645a56 n/a (libgobject-2.0.so.0 + 0x14a56)
#6 0x00007f1ff0664b28 g_signal_emit_valist (libgobject-2.0.so.0 + 0x33b28)
#7 0x00007f1ff06650d3 g_signal_emit (libgobject-2.0.so.0 + 0x340d3)
#8 0x00005562ad7825ec n/a (gnome-calendar + 0x5f5ec)
#9 0x00007f1ff0557e6e g_main_context_dispatch (libglib-2.0.so.0 + 0x51e6e)
#10 0x00007f1ff0558220 n/a (libglib-2.0.so.0 + 0x52220)
#11 0x00007f1ff05582c3 g_main_context_iteration (libglib-2.0.so.0 + 0x522c3)
#12 0x00007f1ff0773fd5 g_application_run (libgio-2.0.so.0 + 0xe2fd5)
#13 0x00005562ad747532 main (gnome-calendar + 0x24532)
#14 0x00007f1ff00010b3 __libc_start_main (libc.so.6 + 0x270b3)
#15 0x00005562ad74757e _start (gnome-calendar + 0x2457e)
Stack trace of thread 249544:
#0 0x00007f1ff00efaff __GI___poll (libc.so.6 + 0x115aff)
#1 0x00007f1ff055818e n/a (libglib-2.0.so.0 + 0x5218e)
#2 0x00007f1ff05582c3 g_main_context_iteration (libglib-2.0.so.0 + 0x522c3)
#3 0x00007f1ff155799d n/a (libdconfsettings.so + 0xa99d)
#4 0x00007f1ff0581911 n/a (libglib-2.0.so.0 + 0x7b911)
#5 0x00007f1fef452609 start_thread (libpthread.so.0 + 0x9609)
#6 0x00007f1ff00fc293 __clone (libc.so.6 + 0x122293)
Stack trace of thread 249543:
#0 0x00007f1ff00efaff __GI___poll (libc.so.6 + 0x115aff)
#1 0x00007f1ff055818e n/a (libglib-2.0.so.0 + 0x5218e)
#2 0x00007f1ff0558513 g_main_loop_run (libglib-2.0.so.0 + 0x52513)
#3 0x00007f1ff07afeda n/a (libgio-2.0.so.0 + 0x11eeda)
#4 0x00007f1ff0581911 n/a (libglib-2.0.so.0 + 0x7b911)
#5 0x00007f1fef452609 start_thread (libpthread.so.0 + 0x9609)
#6 0x00007f1ff00fc293 __clone (libc.so.6 + 0x122293)
Stack trace of thread 249541:
#0 0x00007f1ff00efaff __GI___poll (libc.so.6 + 0x115aff)
#1 0x00007f1ff055818e n/a (libglib-2.0.so.0 + 0x5218e)
#2 0x00007f1ff05582c3 g_main_context_iteration (libglib-2.0.so.0 + 0x522c3)
#3 0x00007f1ff0558311 n/a (libglib-2.0.so.0 + 0x52311)
#4 0x00007f1ff0581911 n/a (libglib-2.0.so.0 + 0x7b911)
#5 0x00007f1fef452609 start_thread (libpthread.so.0 + 0x9609)
#6 0x00007f1ff00fc293 __clone (libc.so.6 + 0x122293)
Stack trace of thread 249582:
#0 0x00007f1ff00efaff __GI___poll (libc.so.6 + 0x115aff)
#1 0x00007f1ff055818e n/a (libglib-2.0.so.0 + 0x5218e)
#2 0x00007f1ff0558513 g_main_loop_run (libglib-2.0.so.0 + 0x52513)
#3 0x00005562ad782541 n/a (gnome-calendar + 0x5f541)
#4 0x00007f1ff0581911 n/a (libglib-2.0.so.0 + 0x7b911)
#5 0x00007f1fef452609 start_thread (libpthread.so.0 + 0x9609)
#6 0x00007f1ff00fc293 __clone (libc.so.6 + 0x122293)
Stack trace of thread 249556:
#0 0x00007f1ff00efaff __GI___poll (libc.so.6 + 0x115aff)
#1 0x00007f1ff055818e n/a (libglib-2.0.so.0 + 0x5218e)
#2 0x00007f1ff0558513 g_main_loop_run (libglib-2.0.so.0 + 0x52513)
#3 0x00007f1ff14d6f98 n/a (libedataserver-1.2.so.24 + 0x70f98)
#4 0x00007f1ff0581911 n/a (libglib-2.0.so.0 + 0x7b911)
#5 0x00007f1fef452609 start_thread (libpthread.so.0 + 0x9609)
#6 0x00007f1ff00fc293 __clone (libc.so.6 + 0x122293)
Stack trace of thread 249583:
#0 0x00007f1ff00efaff __GI___poll (libc.so.6 + 0x115aff)
#1 0x00007f1ff055818e n/a (libglib-2.0.so.0 + 0x5218e)
#2 0x00007f1ff0558513 g_main_loop_run (libglib-2.0.so.0 + 0x52513)
#3 0x00005562ad782541 n/a (gnome-calendar + 0x5f541)
#4 0x00007f1ff0581911 n/a (libglib-2.0.so.0 + 0x7b911)
#5 0x00007f1fef452609 start_thread (libpthread.so.0 + 0x9609)
#6 0x00007f1ff00fc293 __clone (libc.so.6 + 0x122293)
Stack trace of thread 249563:
#0 0x00007f1ff00efaff __GI___poll (libc.so.6 + 0x115aff)
#1 0x00007f1ff055818e n/a (libglib-2.0.so.0 + 0x5218e)
#2 0x00007f1ff0558513 g_main_loop_run (libglib-2.0.so.0 + 0x52513)
#3 0x00007f1ff099f678 n/a (libecal-2.0.so.1 + 0x26678)
#4 0x00007f1ff0581911 n/a (libglib-2.0.so.0 + 0x7b911)
#5 0x00007f1fef452609 start_thread (libpthread.so.0 + 0x9609)
#6 0x00007f1ff00fc293 __clone (libc.so.6 + 0x122293)
Stack trace of thread 249586:
#0 0x00007f1ff00efaff __GI___poll (libc.so.6 + 0x115aff)
#1 0x00007f1ff055818e n/a (libglib-2.0.so.0 + 0x5218e)
#2 0x00007f1ff0558513 g_main_loop_run (libglib-2.0.so.0 + 0x52513)
#3 0x00005562ad782541 n/a (gnome-calendar + 0x5f541)
#4 0x00007f1ff0581911 n/a (libglib-2.0.so.0 + 0x7b911)
#5 0x00007f1fef452609 start_thread (libpthread.so.0 + 0x9609)
#6 0x00007f1ff00fc293 __clone (libc.so.6 + 0x122293)
Stack trace of thread 249579:
#0 0x00007f1ff00efaff __GI___poll (libc.so.6 + 0x115aff)
#1 0x00007f1ff055818e n/a (libglib-2.0.so.0 + 0x5218e)
#2 0x00007f1ff0558513 g_main_loop_run (libglib-2.0.so.0 + 0x52513)
#3 0x00005562ad782541 n/a (gnome-calendar + 0x5f541)
#4 0x00007f1ff0581911 n/a (libglib-2.0.so.0 + 0x7b911)
#5 0x00007f1fef452609 start_thread (libpthread.so.0 + 0x9609)
#6 0x00007f1ff00fc293 __clone (libc.so.6 + 0x122293)
Stack trace of thread 249589:
#0 0x00007f1ff00efaff __GI___poll (libc.so.6 + 0x115aff)
#1 0x00007f1ff055818e n/a (libglib-2.0.so.0 + 0x5218e)
#2 0x00007f1ff0558513 g_main_loop_run (libglib-2.0.so.0 + 0x52513)
#3 0x00005562ad782541 n/a (gnome-calendar + 0x5f541)
#4 0x00007f1ff0581911 n/a (libglib-2.0.so.0 + 0x7b911)
#5 0x00007f1fef452609 start_thread (libpthread.so.0 + 0x9609)
#6 0x00007f1ff00fc293 __clone (libc.so.6 + 0x122293)
Stack trace of thread 249592:
#0 0x00007f1ff00efaff __GI___poll (libc.so.6 + 0x115aff)
#1 0x00007f1ff055818e n/a (libglib-2.0.so.0 + 0x5218e)
#2 0x00007f1ff0558513 g_main_loop_run (libglib-2.0.so.0 + 0x52513)
#3 0x00005562ad782541 n/a (gnome-calendar + 0x5f541)
#4 0x00007f1ff0581911 n/a (libglib-2.0.so.0 + 0x7b911)
#5 0x00007f1fef452609 start_thread (libpthread.so.0 + 0x9609)
#6 0x00007f1ff00fc293 __clone (libc.so.6 + 0x122293)
Stack trace of thread 249574:
#0 0x00007f1ff00f589d syscall (libc.so.6 + 0x11b89d)
#1 0x00007f1ff05a54b6 g_cond_wait_until (libglib-2.0.so.0 + 0x9f4b6)
#2 0x00007f1ff0528541 n/a (libglib-2.0.so.0 + 0x22541)
#3 0x00007f1ff058230a n/a (libglib-2.0.so.0 + 0x7c30a)
#4 0x00007f1ff0581911 n/a (libglib-2.0.so.0 + 0x7b911)
#5 0x00007f1fef452609 start_thread (libpthread.so.0 + 0x9609)
#6 0x00007f1ff00fc293 __clone (libc.so.6 + 0x122293)
Stack trace of thread 249575:
#0 0x00007f1ff00efaff __GI___poll (libc.so.6 + 0x115aff)
#1 0x00007f1ff055818e n/a (libglib-2.0.so.0 + 0x5218e)
#2 0x00007f1ff0558513 g_main_loop_run (libglib-2.0.so.0 + 0x52513)
#3 0x00005562ad782541 n/a (gnome-calendar + 0x5f541)
#4 0x00007f1ff0581911 n/a (libglib-2.0.so.0 + 0x7b911)
#5 0x00007f1fef452609 start_thread (libpthread.so.0 + 0x9609)
#6 0x00007f1ff00fc293 __clone (libc.so.6 + 0x122293)
-- Subject: Process 249540 (gnome-calendar) dumped core
-- Defined-By: systemd
-- Support: http://www.ubuntu.com/support
-- Documentation: man:core(5)
--
-- Process 249540 (gnome-calendar) crashed and dumped core.
--
-- This usually indicates a programming error in the crashing program and
-- should be reported to its vendor as a bug.
Feb 08 01:44:16 saturn systemd[1]: systemd-coredump@41-249641-0.service: Succeeded.
-- Subject: Unit succeeded
-- Defined-By: systemd
-- Support: http://www.ubuntu.com/support
--
-- The unit systemd-coredump@41-249641-0.service has successfully entered the 'dead' state.
Thank you for your bug report but Mint issue should be reported to the corresponding project and not Ubuntu