Here is an extract of the crash report (Can't fit it all in here)
Process: iMovie [2335]
Path: /Applications/iMovie.app/Contents/MacOS/iMovie
Identifier: com.apple.iMovieApp
Version: 10.1.8 (311956)
Build Info: iMovieX-31195006019000000~1
App Item ID: 408981434
App External ID: 824158953
Code Type: X86-64 (Native)
Parent Process: ??? [1]
Responsible: iMovie [2335]
User ID: 501
Date/Time: 2017-11-12 21:25:44.721 +0100
OS Version: Mac OS X 10.13.1 (17B48)
Report Version: 12
Bridge OS Version: 3.0 (14Y661)
Anonymous UUID: 421A7090-25A9-160A-5AD6-B79868E57E81
Time Awake Since Boot: 5700 seconds
System Integrity Protection: enabled
Crashed Thread: 39 Dispatch queue: com.apple.root.default-qos
Exception Type: EXC_CRASH (SIGABRT)
Exception Codes: 0x0000000000000000, 0x0000000000000000
Exception Note: EXC_CORPSE_NOTIFY
Application Specific Information:
-[QCCGLRootContext minimalSharedContextForCurrentThread]: Inconsistent state
abort() called
Application Specific Backtrace 1:
0 CoreFoundation 0x00007fff2df502fb __exceptionPreprocess + 171
1 libobjc.A.dylib 0x00007fff548bdc76 objc_exception_throw + 48
2 CoreFoundation 0x00007fff2df50249 -[NSException raise] + 9
3 QuartzComposer 0x00007fff389e8672 GFException + 278
4 QuartzComposer 0x00007fff389eb5b3 GFThrowException + 292
5 QuartzComposer 0x00007fff3899197f -[QCCGLContext minimalSharedContextForCurrentThread] + 243
6 QuartzComposer 0x00007fff3899155f -[QCOpenGLContext startRenderingPatch:options:] + 61
7 QuartzComposer 0x00007fff389bfdb8 -[QCRenderer initWithRenderingContext:patch:] + 374
8 QuartzComposer 0x00007fff38a3644a -[QCRenderer initOffScreenWithPixelFormat:size:colorSpace:patch:] + 1078
9 QuartzComposer 0x00007fff38a3685b -[QCRenderer initOffScreenWithSize:colorSpace:composition:] + 155
10 Flexo 0x000000010e9232f1 -[FFIMTrailerInfo newThumbnailOfSize:] + 1361
11 Flexo 0x000000010e923477 -[FFIMTrailerInfo thumbnail] + 71
12 Flexo 0x000000010e923630 __50+[FFIMTrailerInfo preloadThumbnailsForTrailerIDs:]_block_invoke + 272
13 libdispatch.dylib 0x00007fff5547a6cd _dispatch_call_block_and_release + 12
14 libdispatch.dylib 0x00007fff55472e88 _dispatch_client_callout + 8
15 libdispatch.dylib 0x00007fff5547fda5 _dispatch_queue_override_invoke + 880
16 libdispatch.dylib 0x00007fff55474a7a _dispatch_root_queue_drain + 515
17 libdispatch.dylib 0x00007fff55474826 _dispatch_worker_thread3 + 101
18 libsystem_pthread.dylib 0x00007fff557361ca _pthread_wqthread + 1387
19 libsystem_pthread.dylib 0x00007fff55735c4d start_wqthread + 13