#0  0x00007fbf3d3a6267 in __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:55
  [Error: ../sysdeps/unix/sysv/linux/raise.c was not found in source tree]
#1  0x00007fbf3d3a7eca in __GI_abort () at abort.c:89
  [Error: abort.c was not found in source tree]
#2  0x00007fbf3d39f03d in __assert_fail_base (fmt=0x7fbf3d501028 "%s%s%s:%u: %s%sAssertion `%s' failed.\n%n", assertion=assertion@entry=0x7fbf3c8a1050 "((*&(&surface->ref_count)->ref_count) > 0)", file=file@entry=0x7fbf3c8a0fe0 "../../../../src/cairo-surface.c", line=line@entry=953, function=function@entry=0x7fbf3c8a1530 <__PRETTY_FUNCTION__.11168> "cairo_surface_destroy") at assert.c:92
  [Error: assert.c was not found in source tree]
#3  0x00007fbf3d39f0f2 in __GI___assert_fail (assertion=0x7fbf3c8a1050 "((*&(&surface->ref_count)->ref_count) > 0)", file=0x7fbf3c8a0fe0 "../../../../src/cairo-surface.c", line=953, function=0x7fbf3c8a1530 <__PRETTY_FUNCTION__.11168> "cairo_surface_destroy") at assert.c:101
  [Error: assert.c was not found in source tree]
#4  0x00007fbf3c833212 in INT_cairo_surface_destroy (surface=0xcdf) at ../../../../src/cairo-surface.c:953
  [Error: ../../../../src/cairo-surface.c was not found in source tree]
#5  0x00007fbf3c863080 in _get_image_surface (surface=0x1203e00, extents=0x7ffe3d289230, try_shm=18874442) at ../../../../src/cairo-xlib-surface.c:1014
  [Error: ../../../../src/cairo-xlib-surface.c was not found in source tree]
#6  0x00007fbf3c863d13 in _cairo_xlib_surface_acquire_source_image (abstract_surface=0x1203e00, image_out=0x7ffe3d2892f0, image_extra=<optimized out>) at ../../../../src/cairo-xlib-surface.c:1403
  [Error: ../../../../src/cairo-xlib-surface.c was not found in source tree]
#7  0x00007fbf3c833ad4 in _cairo_surface_acquire_source_image (surface=0x1203e00, image_out=<optimized out>, image_extra=<optimized out>) at ../../../../src/cairo-surface.c:1973
  [Error: ../../../../src/cairo-surface.c was not found in source tree]
#8  0x00007fbf3c7fc455 in _pixman_image_for_surface (iy=0x7ffe3d2894d0, ix=0x7ffe3d2894c0, sample=<optimized out>, extents=0x7ffe3d289c2c, is_mask=<optimized out>, pattern=0x7ffe3d289d88, dst=<optimized out>) at ../../../../src/cairo-image-source.c:1377
  [Error: ../../../../src/cairo-image-source.c was not found in source tree]
#9  _pixman_image_for_pattern (dst=<optimized out>, pattern=0x7ffe3d289d88, is_mask=<optimized out>, extents=0x7ffe3d289c2c, sample=<optimized out>, tx=0x7ffe3d2894c0, ty=0x7ffe3d2894d0) at ../../../../src/cairo-image-source.c:1538
  [Error: ../../../../src/cairo-image-source.c was not found in source tree]
#10 0x00007fbf3c7fcf6e in _cairo_image_source_create_for_pattern (dst=0xcdf, pattern=0x7ffe3d289d88, is_mask=1, extents=0x7ffe3d289c2c, sample=0x7ffe3d289c60, src_x=0x1, src_y=0x7ffe3d2894d0) at ../../../../src/cairo-image-source.c:1583
  [Error: ../../../../src/cairo-image-source.c was not found in source tree]
#11 0x00007fbf3c830758 in composite_aligned_boxes (boxes=<optimized out>, extents=<optimized out>, compositor=<optimized out>) at ../../../../src/cairo-spans-compositor.c:651
  [Error: ../../../../src/cairo-spans-compositor.c was not found in source tree]
#12 clip_and_composite_boxes (compositor=0x7fbf3cad9180 <spans>, extents=0x7ffe3d289bf0, boxes=0x7ffe3d289960) at ../../../../src/cairo-spans-compositor.c:882
  [Error: ../../../../src/cairo-spans-compositor.c was not found in source tree]
#13 0x00007fbf3c830abe in clip_and_composite_boxes (compositor=0x7fbf3cad9180 <spans>, extents=0x7ffe3d289bf0, boxes=0x7ffe3d289960) at ../../../../src/cairo-spans-compositor.c:901
  [Error: ../../../../src/cairo-spans-compositor.c was not found in source tree]
#14 0x00007fbf3c830b39 in _cairo_spans_compositor_mask (_compositor=0x7fbf3cad9180 <spans>, extents=0x7ffe3d289bf0) at ../../../../src/cairo-spans-compositor.c:999
  [Error: ../../../../src/cairo-spans-compositor.c was not found in source tree]
#15 0x00007fbf3c7ebcc9 in _cairo_compositor_mask (compositor=0x7fbf3cad9180 <spans>, surface=0xf751f0, op=<optimized out>, source=<optimized out>, mask=<optimized out>, clip=<optimized out>) at ../../../../src/cairo-compositor.c:106
  [Error: ../../../../src/cairo-compositor.c was not found in source tree]
#16 0x00007fbf3c833fbc in _cairo_surface_mask (surface=0xf751f0, op=CAIRO_OPERATOR_OVER, source=0x7ffe3d289f70, mask=0x7ffe3d28a090, clip=0x0) at ../../../../src/cairo-surface.c:2166
  [Error: ../../../../src/cairo-surface.c was not found in source tree]
#17 0x00007fbf3c7f3a44 in _cairo_gstate_mask (gstate=0x1187830, mask=0x1259970) at ../../../../src/cairo-gstate.c:1142
  [Error: ../../../../src/cairo-gstate.c was not found in source tree]
#18 0x00007fbf3c7e66d1 in INT_cairo_mask (cr=0xcdf, cr@entry=0x1187800, pattern=0xcdf, pattern@entry=0x1259970) at ../../../../src/cairo.c:2066
  [Error: ../../../../src/cairo.c was not found in source tree]
#19 0x00007fbf3c7e6786 in cairo_mask_surface (cr=0x1187800, surface=<optimized out>, surface_x=0, surface_y=0) at ../../../../src/cairo.c:2103
  [Error: ../../../../src/cairo.c was not found in source tree]
#20 0x00007fbf3f227c24 in ?? () from /tmp/apport_sandbox_bU5mwT/usr/lib/x86_64-linux-gnu/libwnck-3.so.0
#21 0x00007fbf3f2290c7 in ?? () from /tmp/apport_sandbox_bU5mwT/usr/lib/x86_64-linux-gnu/libwnck-3.so.0
#22 0x00007fbf3f21ebef in ?? () from /tmp/apport_sandbox_bU5mwT/usr/lib/x86_64-linux-gnu/libwnck-3.so.0
#23 0x00007fbf3f21f7d0 in ?? () from /tmp/apport_sandbox_bU5mwT/usr/lib/x86_64-linux-gnu/libwnck-3.so.0
#24 0x00007fbf3f220a25 in ?? () from /tmp/apport_sandbox_bU5mwT/usr/lib/x86_64-linux-gnu/libwnck-3.so.0
#25 0x00007fbf3f21396e in ?? () from /tmp/apport_sandbox_bU5mwT/usr/lib/x86_64-linux-gnu/libwnck-3.so.0
#26 0x00007fbf3f2146c4 in ?? () from /tmp/apport_sandbox_bU5mwT/usr/lib/x86_64-linux-gnu/libwnck-3.so.0
#27 0x00007fbf3d9a2b4d in g_main_dispatch (context=0xeb6260) at /build/buildd/glib2.0-2.44.1/./glib/gmain.c:3122
  [Error: /build/buildd/glib2.0-2.44.1/./glib/gmain.c was not found in source tree]
#28 g_main_context_dispatch (context=context@entry=0xeb6260) at /build/buildd/glib2.0-2.44.1/./glib/gmain.c:3737
  [Error: /build/buildd/glib2.0-2.44.1/./glib/gmain.c was not found in source tree]
#29 0x00007fbf3d9a2f20 in g_main_context_iterate (context=0xeb6260, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at /build/buildd/glib2.0-2.44.1/./glib/gmain.c:3808
  [Error: /build/buildd/glib2.0-2.44.1/./glib/gmain.c was not found in source tree]
#30 0x00007fbf3d9a3242 in g_main_loop_run (loop=0xf058c0) at /build/buildd/glib2.0-2.44.1/./glib/gmain.c:4002
  [Error: /build/buildd/glib2.0-2.44.1/./glib/gmain.c was not found in source tree]
#31 0x00000000004122f1 in main ()