Comment 2 for bug 961119

StacktraceTop:
 g_assertion_message (domain=<optimized out>, file=<optimized out>, line=<optimized out>, func=0x6f0040 "view_collection_real_notify_items_removed", message=0x28f2650 "assertion failed: (_tmp14_)") at /build/buildd/glib2.0-2.31.22/./glib/gtestutils.c:1860
 g_assertion_message_expr (domain=0x0, file=0x6ee928 "/build/buildd/shotwell-0.11.93/src/core/ViewCollection.vala", line=573, func=0x6f0040 "view_collection_real_notify_items_removed", expr=<optimized out>) at /build/buildd/glib2.0-2.31.22/./glib/gtestutils.c:1871
 view_collection_real_notify_items_removed (base=<optimized out>, removed=0x7f029c002b30) at /build/buildd/shotwell-0.11.93/src/core/ViewCollection.vala:573
 data_collection_real_clear (self=0x312f490) at /build/buildd/shotwell-0.11.93/src/core/DataCollection.vala:478
 data_collection_real_clear (self=0x312f490) at DataCollection.c:1981