Changing font in preferences shuts down program

When trying to change the font under the Browser tab in preferences the application crashes. this is on a Mac, with latest OS version, as soon as I place a font size, or select it (using 12) it just crashes. I've included a screenshot of the area I was in. I can replicate this multiple times.

Part of the OS error log is shown below:

rocess: Ultra Fractal [737]
Path: /Applications/Ultra Fractal.app/Contents/MacOS/Ultra Fractal
Identifier: com.ultrafractal.UltraFractal.5
Version: 5.55 (5.5.5)
Code Type: X86 (Native)
Parent Process: ??? [1]
Responsible: Ultra Fractal [737]
User ID: 501

Date/Time: 2017-09-14 07:36:35.273 -0700
OS Version: Mac OS X 10.12.6 (16G29)
Report Version: 12
Anonymous UUID: B5D55D5A-CFB9-CED4-F025-A1C5C68FA076

Time Awake Since Boot: 3000 seconds

System Integrity Protection: enabled

Crashed Thread: 0 Dispatch queue: com.apple.main-thread

Exception Type: EXC_BREAKPOINT (SIGTRAP)
Exception Codes: 0x0000000000000002, 0x0000000000000000
Exception Note: EXC_CORPSE_NOTIFY

Termination Signal: Trace/BPT trap: 5
Termination Reason: Namespace SIGNAL, Code 0x5
Terminating Process: exc handler [0]
[NSAnimation(NSInternal) _animationThread] + 76
9 com.apple.AppKit 0x920bb74c __42-[NSAnimation(NSInternal) _runInNewThread]_block_invoke + 32

Thanks for the report, I'll try to reproduce the problem myself.

I get the crash as well. Will be fixed in the next release.