CRASH: MIKMIDIEventIterator can crash with EXC_BAD_ACCESS during MIKMIDISequencer playback

[kris2point0]

Setting a MIKMIDISequencer instance's sequence during playback can sometimes result in a crash in MIKMIDIEventIterator.

Thread 12 Crashed:: Dispatch queue: com.mixedinkey.SkyStage.MIKStudioMIDISequencer.0x61800019ce50
0   com.apple.audio.toolbox.AudioToolbox    0x00007fff9b3ef7e8 TrackIterator::Seek(double) + 44
1   com.apple.audio.toolbox.AudioToolbox    0x00007fff9b3ea1ff MusicEventIteratorSeek + 35
2   com.mixedinkey.MIKMIDI          0x000000010435cb4d -[MIKMIDIEventIterator seek:] + 42
3   com.mixedinkey.MIKMIDI          0x0000000104341626 -[MIKMIDITrack private_eventsOfClass:fromTimeStamp:toTimeStamp:] + 89
4   com.mixedinkey.MIKMIDI          0x0000000104356eb3 -[MIKMIDISequencer processSequenceStartingFromMIDITimeStamp:] + 2532
5   libdispatch.dylib               0x00007fff963c6c13 _dispatch_client_callout + 8
6   libdispatch.dylib               0x00007fff963d187e _dispatch_source_latch_and_call + 721
7   libdispatch.dylib               0x00007fff963ca62b _dispatch_source_invoke + 412
8   libdispatch.dylib               0x00007fff963ca154 _dispatch_queue_drain + 571
9   libdispatch.dylib               0x00007fff963cbecc _dispatch_queue_invoke + 202
10  libdispatch.dylib               0x00007fff963c96b7 _dispatch_root_queue_drain + 463
11  libdispatch.dylib               0x00007fff963d7fe4 _dispatch_worker_thread3 + 91
12  libsystem_pthread.dylib         0x00007fff92fbb637 _pthread_wqthread + 729
13  libsystem_pthread.dylib         0x00007fff92fb940d start_wqthread + 13

At this point, creating a new iterator in LLDB and attempting a seek has the same failure.

(lldb) expr MIKMIDIEventIterator *$i2 = [MIKMIDIEventIterator iteratorForTrack:self]
(lldb) po $i2
<MIKMIDIEventIterator: 0x6080000039b0>

(lldb) expr [$i2 seek:11.82]
error: Execution was interrupted, reason: EXC_BAD_ACCESS (code=1, address=0x119ffffe0).
The process has been returned to the state before expression evaluation.

So far, I've only encoutered this in tracks that have 0 events. So for now, I'm going to attempt to workaround the issue in -[MIKMIDITrack private_eventsOfClass:fromTimeStamp:toTimeStamp:] by first checking if there are any events in the track.

[armadsen]

This seems to be effectively prevented by the workaround in cb30667. Closing for now.