Indeed, it hits an invalid free it seems

==17180== Invalid free() / delete / delete[] / realloc()
==17180==    at 0x402D378: free (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
==17180==    by 0x51CC16F: g_free (in /lib/i386-linux-gnu/libglib-2.0.so.0.4600.1)
==17180==    by 0x504E049: g_local_file_trash (in /usr/lib/i386-linux-gnu/libgio-2.0.so.0.4600.1)
==17180==    by 0x4F9CA8D: g_file_trash (in /usr/lib/i386-linux-gnu/libgio-2.0.so.0.4600.1)
==17180==    by 0x80F191F: trash_files (nautilus-file-operations.c:1930)
==17180==    by 0x80F191F: delete_job (nautilus-file-operations.c:2113)
==17180==    by 0x4FB451A: io_job_thread (in /usr/lib/i386-linux-gnu/libgio-2.0.so.0.4600.1)
==17180==    by 0x4FDBB57: g_task_thread_pool_thread (in /usr/lib/i386-linux-gnu/libgio-2.0.so.0.4600.1)
==17180==    by 0x51EE833: g_thread_pool_thread_proxy (in /lib/i386-linux-gnu/libglib-2.0.so.0.4600.1)
==17180==    by 0x51EDDD9: g_thread_proxy (in /lib/i386-linux-gnu/libglib-2.0.so.0.4600.1)
==17180==    by 0x53431A9: start_thread (pthread_create.c:333)
==17180==    by 0x5444FDD: clone (clone.S:122)
==17180==  Address 0xee721c8 is 0 bytes inside a block of size 24 free'd
==17180==    at 0x402D378: free (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
==17180==    by 0x51CC16F: g_free (in /lib/i386-linux-gnu/libglib-2.0.so.0.4600.1)
==17180==    by 0x504DE11: g_local_file_trash (in /usr/lib/i386-linux-gnu/libgio-2.0.so.0.4600.1)
==17180==    by 0x4F9CA8D: g_file_trash (in /usr/lib/i386-linux-gnu/libgio-2.0.so.0.4600.1)
==17180==    by 0x80F191F: trash_files (nautilus-file-operations.c:1930)
==17180==    by 0x80F191F: delete_job (nautilus-file-operations.c:2113)
==17180==    by 0x4FB451A: io_job_thread (in /usr/lib/i386-linux-gnu/libgio-2.0.so.0.4600.1)
==17180==    by 0x4FDBB57: g_task_thread_pool_thread (in /usr/lib/i386-linux-gnu/libgio-2.0.so.0.4600.1)
==17180==    by 0x51EE833: g_thread_pool_thread_proxy (in /lib/i386-linux-gnu/libglib-2.0.so.0.4600.1)
==17180==    by 0x51EDDD9: g_thread_proxy (in /lib/i386-linux-gnu/libglib-2.0.so.0.4600.1)
==17180==    by 0x53431A9: start_thread (pthread_create.c:333)
==17180==    by 0x5444FDD: clone (clone.S:122)
==17180==  Block was alloc'd at
==17180==    at 0x402C19C: malloc (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
==17180==    by 0x51CC048: g_malloc (in /lib/i386-linux-gnu/libglib-2.0.so.0.4600.1)
==17180==    by 0x51E54BD: g_strdup (in /lib/i386-linux-gnu/libglib-2.0.so.0.4600.1)
==17180==    by 0x504D6B8: find_mountpoint_for (in /usr/lib/i386-linux-gnu/libgio-2.0.so.0.4600.1)
==17180==    by 0x504D97D: g_local_file_trash (in /usr/lib/i386-linux-gnu/libgio-2.0.so.0.4600.1)
==17180==    by 0x4F9CA8D: g_file_trash (in /usr/lib/i386-linux-gnu/libgio-2.0.so.0.4600.1)
==17180==    by 0x80F191F: trash_files (nautilus-file-operations.c:1930)
==17180==    by 0x80F191F: delete_job (nautilus-file-operations.c:2113)
==17180==    by 0x4FB451A: io_job_thread (in /usr/lib/i386-linux-gnu/libgio-2.0.so.0.4600.1)
==17180==    by 0x4FDBB57: g_task_thread_pool_thread (in /usr/lib/i386-linux-gnu/libgio-2.0.so.0.4600.1)
==17180==    by 0x51EE833: g_thread_pool_thread_proxy (in /lib/i386-linux-gnu/libglib-2.0.so.0.4600.1)
==17180==    by 0x51EDDD9: g_thread_proxy (in /lib/i386-linux-gnu/libglib-2.0.so.0.4600.1)
==17180==    by 0x53431A9: start_thread (pthread_create.c:333)
==17180==    by 0x5444FDD: clone (clone.S:122)