Description of problem:
I tried to enable gtk inspector (ctrl+shift+d) in gtk3-demo. When I tried it again, it worked correctly.

Version-Release number of selected component:
gtk3-devel-3.19.4-1.fc24

Additional info:
reporter:       libreport-2.6.3
backtrace_rating: 4
cmdline:        gtk3-demo
crash_function: g_type_check_instance_is_a
executable:     /usr/bin/gtk3-demo
global_pid:     21952
kernel:         4.4.0-0.rc4.git4.1.fc24.x86_64
runlevel:       N 5
type:           CCpp
uid:            1000

Truncated backtrace:
Thread no. 1 (10 frames)
 #0 g_type_check_instance_is_a at gtype.c:4021
 #1 gtk_widget_get_scale_factor at gtkwidget.c:10957
 #2 gtk_css_widget_node_get_style_provider at gtkcsswidgetnode.c:244
 #3 gtk_css_node_get_style_provider_or_null at gtkcssnode.c:103
 #4 gtk_css_node_invalidate_style_provider at gtkcssnode.c:1279
 #13 _gtk_style_provider_private_changed at gtkstyleproviderprivate.c:113
 #14 gtk_css_provider_load_from_file at gtkcssprovider.c:2942
 #15 gtk_css_provider_load_from_resource at gtkcssprovider.c:3012
 #16 _gtk_css_provider_load_named at gtkcssprovider.c:3179
 #17 settings_update_theme at gtksettings.c:3212