Crash with view setting

[duboz]

Irritator crashes after the following actions:

• unselect "View" -> "Fix window layout".
• Reduce the "Component library" window by clicking the invert triangle left to the window's name.

gdb backtrace:
#0 0x00007ffff7a46a7c in pthread_kill () from /lib/x86_64-linux-gnu/libc.so.6
#1 0x00007ffff79f2476 in raise () from /lib/x86_64-linux-gnu/libc.so.6
#2 0x00007ffff79d87f3 in abort () from /lib/x86_64-linux-gnu/libc.so.6
#3 0x00007ffff79d871b in ?? () from /lib/x86_64-linux-gnu/libc.so.6
#4 0x00007ffff79e9e96 in __assert_fail () from /lib/x86_64-linux-gnu/libc.so.6
#5 0x0000555555b8e74a in ImGui::ErrorCheckEndFrameSanityChecks() ()
#6 0x0000555555b8244f in ImGui::EndFrame() ()
#7 0x0000555555b828b0 in ImGui::Render() ()
#8 0x0000555555c34322 in main ()