Downstream report: 

https://bugzilla.redhat.com/show_bug.cgi?id=926893

Setting your font to Abyssibicia SIL at least, and then selecting the 'open with other application' causes Thunar to crash. 

#8 allocator_memalign at gslice.c:1381
 #9 allocator_add_slab at gslice.c:1252
 #10 slab_allocator_alloc_chunk at gslice.c:1300
 #11 magazine_cache_pop_magazine at gslice.c:724
 #12 thread_memory_magazine1_reload at gslice.c:794
 #13 g_slice_alloc at gslice.c:992
 #14 pango_item_copy at pango-item.c:62
 #15 pango_item_split at pango-item.c:146
 #16 process_item at pango-layout.c:3420
 #17 process_line at pango-layout.c:3595