Here is the crash report of your own example (part of it).
Process: Mein Programm [973]
Path: /Users/USER/Desktop/*/Mein Programm.app/Contents/MacOS/Mein Programm
Identifier: touchbar.test
Version: ??? (1.0.0.0.0)
Code Type: X86-64 (Native)
Parent Process: ??? [1]
Responsible: Mein Programm [973]
User ID: 502
Date/Time: 2016-11-20 18:09:04.211 +0100
OS Version: Mac OS X 10.12.1 (16B2657)
Report Version: 12
Anonymous UUID: DE211587-E425-5BC2-4643-05615351EDDD
Sleep/Wake UUID: 93BA6248-30FB-429B-99F6-EFABD63AAB62
Time Awake Since Boot: 4000 seconds
Time Since Wake: 2300 seconds
System Integrity Protection: enabled
Crashed Thread: 0 Dispatch queue: com.apple.main-thread
Exception Type: EXC_BAD_ACCESS (SIGSEGV)
Exception Codes: KERN_INVALID_ADDRESS at 0x00004c19a8a8bec0
Exception Note: EXC_CORPSE_NOTIFY
Termination Signal: Segmentation fault: 11
Termination Reason: Namespace SIGNAL, Code 0xb
Terminating Process: exc handler [0]
VM Regions Near 0x4c19a8a8bec0:
__LINKEDIT 000000011270d000-0000000112723000 [ 88K] r–/rwx SM=COW /usr/lib/dyld
–>
MALLOC_NANO 0000600000000000-0000600000400000 [ 4096K] rw-/rwx SM=PRV
Application Specific Information:
objc_msgSend() selector name: removeObserver:forKeyPath:
Thread 0 Crashed:: Dispatch queue: com.apple.main-thread
0 libobjc.A.dylib 0x00007fffd0d15b5d objc_msgSend + 29
1 MBS_TouchBar_Plugin_19182.dylib 0x000000010ca13368 -[MyNSTouchBarDelegateMBS clearTarget] + 56
2 MBS_TouchBar_Plugin_19182.dylib 0x000000010ca117b1 NSTouchBarDestructor(REALobjectStruct*) + 129
3 touchbar.test 0x000000010a699446 NSTouchBarMBS.__exit%%o + 54
4 com.xojo.XojoFramework 0x000000010ab1d9ec RuntimeUnlockObject + 792
5 touchbar.test 0x000000010a6aa541 App.BuildAppTouchBar%%o + 2289
6 touchbar.test 0x000000010a6a9b8b App.Event_Open%%o + 155
7 com.xojo.XojoFramework 0x000000010a9b76fb 0x10a979000 + 255739
8 com.xojo.XojoFramework 0x000000010a9b6354 0x10a979000 + 250708
9 com.apple.CoreFoundation 0x00007fffbc30c5ec CFNOTIFICATIONCENTER_IS_CALLING_OUT_TO_AN_OBSERVER + 12
10 com.apple.CoreFoundation 0x00007fffbc30c4eb _CFXRegistrationPost + 427
11 com.apple.CoreFoundation 0x00007fffbc30c252 ___CFXNotificationPost_block_invoke + 50
12 com.apple.CoreFoundation 0x00007fffbc2ca972 -[_CFXNotificationRegistrar find:object:observer:enumerator:] + 2018
13 com.apple.CoreFoundation 0x00007fffbc2c995b _CFXNotificationPost + 667
14 com.apple.Foundation 0x00007fffbdcf70e3 -[NSNotificationCenter postNotificationName:object:userInfo:] + 66
15 com.apple.AppKit 0x00007fffb9fca03d -[NSApplication _postDidFinishNotification] + 297
16 com.apple.AppKit 0x00007fffb9fc9da2 -[NSApplication _sendFinishLaunchingNotification] + 208
17 com.apple.AppKit 0x00007fffb9e88a7b _DPSNextEvent + 2035
18 com.apple.AppKit 0x00007fffba5ff830 -[NSApplication(NSEvent) _nextEventMatchingEventMask:untilDate:inMode:dequeue:] + 2730
19 com.xojo.XojoFramework 0x000000010a9b7e17 0x10a979000 + 257559
20 com.xojo.XojoFramework 0x000000010a9b7e5b 0x10a979000 + 257627
21 touchbar.test 0x000000010a54dcf7 Delegate.Invoke%% + 7
22 touchbar.test 0x000000010a4c91d1 Application._CallFunctionWithExceptionHandling%%op + 273
23 com.xojo.XojoFramework 0x000000010ab1bdeb 0x10a979000 + 1715691
24 com.xojo.XojoFramework 0x000000010a9b7db4 0x10a979000 + 257460
25 com.apple.AppKit 0x00007fffb9e7d06d -[NSApplication run] + 926
26 com.xojo.XojoFramework 0x000000010ab1a1bb RuntimeRun + 40
27 touchbar.test 0x000000010a5269b8 REALbasic._RuntimeRun + 24
28 touchbar.test 0x000000010a6b8d4a _Main + 538
29 touchbar.test 0x000000010a6b8471 main + 65
30 touchbar.test 0x000000010a489bc4 start + 52
Thread 1:
0 libsystem_kernel.dylib 0x00007fffd172f4e6 __workq_kernreturn + 10
1 libsystem_pthread.dylib 0x00007fffd18177b5 _pthread_wqthread + 1426
2 libsystem_pthread.dylib 0x00007fffd1817211 start_wqthread + 13
Thread 2:
0 libsystem_kernel.dylib 0x00007fffd172f4e6 __workq_kernreturn + 10
1 libsystem_pthread.dylib 0x00007fffd18177b5 _pthread_wqthread + 1426
2 libsystem_pthread.dylib 0x00007fffd1817211 start_wqthread + 13
Thread 3:
0 libsystem_kernel.dylib 0x00007fffd172f4e6 __workq_kernreturn + 10
1 libsystem_pthread.dylib 0x00007fffd18177b5 _pthread_wqthread + 1426
2 libsystem_pthread.dylib 0x00007fffd1817211 start_wqthread + 13
Thread 4:
0 libsystem_kernel.dylib 0x00007fffd172f4e6 __workq_kernreturn + 10
1 libsystem_pthread.dylib 0x00007fffd18177b5 _pthread_wqthread + 1426
2 libsystem_pthread.dylib 0x00007fffd1817211 start_wqthread + 13
Thread 5:
0 libsystem_kernel.dylib 0x00007fffd172f4e6 __workq_kernreturn + 10
1 libsystem_pthread.dylib 0x00007fffd1817622 _pthread_wqthread + 1023
2 libsystem_pthread.dylib 0x00007fffd1817211 start_wqthread + 13
Thread 6:
0 libsystem_kernel.dylib 0x00007fffd172f4e6 __workq_kernreturn + 10
1 libsystem_pthread.dylib 0x00007fffd18177b5 _pthread_wqthread + 1426
2 libsystem_pthread.dylib 0x00007fffd1817211 start_wqthread + 13
Thread 7:
0 libsystem_kernel.dylib 0x00007fffd172f4e6 __workq_kernreturn + 10
1 libsystem_pthread.dylib 0x00007fffd1817622 _pthread_wqthread + 1023
2 libsystem_pthread.dylib 0x00007fffd1817211 start_wqthread + 13
Thread 0 crashed with X86 Thread State (64-bit):
rax: 0x0000000000000001 rbx: 0x000060000002cce0 rcx: 0x000000010ca202a8 rdx: 0x000060000002cce0
rdi: 0x0000600000087ee0 rsi: 0x00007fffbaaacc7a rbp: 0x00007fff55775490 rsp: 0x00007fff55775468
r8: 0x0000000000000050 r9: 0x0000600000087ee0 r10: 0x00004c19a8a8bea8 r11: 0x00007fffbaaacc7a
r12: 0x000000010ad1fca8 r13: 0x0000610000287f38 r14: 0x0000000000000010 r15: 0x00007fffd0d15b40
rip: 0x00007fffd0d15b5d rfl: 0x0000000000010202 cr2: 0x00004c19a8a8bec0
Logical CPU: 4
Error Code: 0x00000004
Trap Number: 14