Bug#1020663: GIMP crashes when trying to using test tool

[Bernhard Übelacker]

> #6  0x00007faef481caa0 in <signal handler called> () at /lib/x86_64-linux-gnu/libc.so.6
> #7  0x00007faef4c1c103 in  () at /lib/x86_64-linux-gnu/libgobject-2.0.so.0
> #8  0x00007faef4c126d8 in  () at /lib/x86_64-linux-gnu/libgobject-2.0.so.0
> #9  0x00007faef4c12f5a in  () at /lib/x86_64-linux-gnu/libgobject-2.0.so.0
> #10 0x00007faef4c143f4 in g_object_new_with_properties () at /lib/x86_64-linux-gnu/libgobject-2.0.so.0
> #11 0x000055cae69d0787 in gimp_image_undo_push ()
> #12 0x000055cae69d3344 in gimp_image_undo_push_text_layer ()
> #13 0x000055cae6702e93 in gimp_text_tool_apply ()


Frames below signal handler are looking similar to #1018105.