First time using Unibeast, and I'm running into the same problem. Using Unibeast 5.2.0 on OS X Yosemite 10.10.4, something to do with populating an array?
2015-07-16 14:41:26.774 UniBeast[11800:1182880] *** -[__NSArrayI objectAtIndex:]: index 1 beyond bounds [0 .. 0]
2015-07-16 14:41:26.776 UniBeast[11800:1182880] (
0 CoreFoundation 0x00007fff8db4403c __exceptionPreprocess + 172
1 libobjc.A.dylib 0x00007fff93da476e objc_exception_throw + 43
2 CoreFoundation 0x00007fff8da1bbce -[__NSArrayI objectAtIndex:] + 190
3 UniBeast 0x00000001000026df UniBeast + 9951
4 AppKit 0x00007fff881da2bd -[NSAlert didEndAlert:returnCode:contextInfo:] + 90
5 AppKit 0x00007fff87fde586 -[NSWindow _endWindowBlockingModalSession:returnCode:] + 315
6 AppKit 0x00007fff8806dd97 -[NSAlert buttonPressed:] + 107
7 libsystem_trace.dylib 0x00007fff868bfcd7 _os_activity_initiate + 75
8 AppKit 0x00007fff87fb0eb1 -[NSApplication sendAction:to:from:] + 452
9 AppKit 0x00007fff87fc6946 -[NSControl sendAction:to:] + 86
10 AppKit 0x00007fff87fc6862 __26-[NSCell _sendActionFrom:]_block_invoke + 131
11 libsystem_trace.dylib 0x00007fff868bfcd7 _os_activity_initiate + 75
12 AppKit 0x00007fff87fc67bf -[NSCell _sendActionFrom:] + 144
13 libsystem_trace.dylib 0x00007fff868bfcd7 _os_activity_initiate + 75
14 AppKit 0x00007fff87fc4cb3 -[NSCell trackMouse:inRect
fView:untilMouseUp:] + 2821
15 AppKit 0x00007fff8801d34f -[NSButtonCell trackMouse:inRect
fView:untilMouseUp:] + 770
16 AppKit 0x00007fff87fc3366 -[NSControl mouseDown:] + 714
17 AppKit 0x00007fff8852d2dc -[NSWindow _reallySendEvent:isDelayedEvent:] + 14125
18 AppKit 0x00007fff87ebcc86 -[NSWindow sendEvent:] + 470
19 AppKit 0x00007fff87eb9212 -[NSApplication sendEvent:] + 2504
20 AppKit 0x00007fff87de2b68 -[NSApplication run] + 711
21 AppKit 0x00007fff87d5f244 NSApplicationMain + 1832
22 UniBeast 0x0000000100001590 UniBeast + 5520