Random crash on closing OTFVis

[michaz]

The JVM spectacularly segfaults when closing the "Simulate..." window, about 20% of the time.

# A fatal error has been detected by the Java Runtime Environment:
#
#  SIGSEGV (0xb) at pc=0x00007fff9be554dd, pid=71768, tid=2571
#
# JRE version: Java(TM) SE Runtime Environment (8.0_74-b02) (build 1.8.0_74-b02)
# Java VM: Java HotSpot(TM) 64-Bit Server VM (25.74-b02 mixed mode bsd-amd64 compressed oops)
# Problematic frame:
# C  [libobjc.A.dylib+0x14dd]  objc_msgSend+0x1d
#
# Failed to write core dump. Core dumps have been disabled. To enable core dumping, try "ulimit -c unlimited" before starting Java again
#
# An error report file with more information is saved as:
# /Users/michaelzilske/git/josm-matsim-plugin/hs_err_pid71768.log 

OK, so perhaps mixing Swing, JavaFX and OpenGL is a little demanding. :-)