xcode crashes after opening the sea creator project

After downloading the sea creator project, found here:
https://developer.apple.com/documentation/safariservices/safari_web_extensions/developing_a_safari_web_extension

Opening it in XCode immediately crashes XCode itself. Running XCode Version 12.0 beta 5 on mac catalina 10.15.6.

This is the error log I'm getting:

Application Specific Information:
ProductBuildVersion: 12A8189h
UNCAUGHT EXCEPTION (NSInvalidArgumentException): -[_NSCFString replaceCharactersInRange:withString:]: nil argument
UserInfo: (null)
Open FDs: 27/4864
Hints:

Backtrace:
0 exceptionPreprocess (in CoreFoundation)
1 DVTFailureHintExceptionPreprocessor (in DVTFoundation)
2 objcexceptionthrow (in libobjc.A.dylib)
3 -[NSCFString characterAtIndex:].cold.1 (in CoreFoundation)
4 mutateError.cold.4 (in CoreFoundation)
5 mutateError (in CoreFoundation)
6 -[NSCFString replaceCharactersInRange:withString:] (in CoreFoundation)
7 -[NSConcreteMutableAttributedString replaceCharactersInRange:withString:] (in Foundation)
8 -[NSMutableAttributedString(DVTNSAttributedStringAdditions) dvtappendString:withAttributes:] (in DVTCocoaAdditionsKit)
9 +[IDEDocumentController informativeTextForQuarantineProperties:] (in IDEKit)
10 +[IDEDocumentController shouldOpenItemAtURLWithSynchronousQuarantinePrompt:documentType:] (in IDEKit)
11 -[IDEDocumentController openProjectsPlaygroundsAndWorkspaces:display:openedDocuments:simpleFileDocumentLocations:completionHandler:] (in IDEKit)
12 -[IDEDocumentController openProjectsPlaygroundsAndWorkspaces:display:completionHandler:] (in IDEKit)
13 -[IDEDocumentController openDocumentsForDocumentLocations:display:completionHandler:] (in IDEKit)
14 -[IDEDocumentController asyncOpenDocumentsWithContentsOfURLs:display:completionHandler:] (in IDEKit)
15 -[IDEApplicationController openURLs:completionBlock:] (in IDEKit)
16 -[IDEApplicationController application:openFiles:] (in IDEKit)
17 withWindowOrderingObserverHeuristic (in AppKit)
18 -[NSApplication(NSAppleEventHandling) openURLs:withCompletionHandler:] (in AppKit)
19 _69-[NSApplication(NSAppleEventHandling) handleAEOpenDocumentsForURLs:]blockinvoke (in AppKit)
20 _90-[NSDocumentController(NSInternal) autoreopenDocumentsFromRecords:withCompletionHandler:]blockinvoke (in AppKit)
21 -[NSDocumentController(NSInternal) autoreopenDocumentsFromRecords:withCompletionHandler:] (in AppKit)
22 97-[NSDocumentController(NSInternal) autoreopenDocumentsIgnoringExpendable:withCompletionHandler:]blockinvoke3 (in AppKit)
23 -[NSDocumentController(NSInternal) autoreopenDocumentsIgnoringExpendable:withCompletionHandler:] (in AppKit)
24 -[NSApplication reopenWindowsAsNecessaryIncludingRestorableState:completionHandler:] (in AppKit)
25 -[NSApplication(NSAppleEventHandling) handleAEOpenDocumentsForURLs:] (in AppKit)
26 -[NSApplication(NSAppleEventHandling) handleCoreEvent:withReplyEvent:] (in AppKit)
27 -[NSAppleEventManager dispatchRawAppleEvent:withRawReply:handlerRefCon:] (in Foundation)
28 -[NSAppleEventManager(DVTAssertionOverrides) swizzleDispatchRawAppleEvent:withRawReply:handlerRefCon:] (in IDEKit)
29 NSAppleEventManagerGenericHandler (in Foundation)
30 HandleOpenDocAE (in IDEKit)
31 0x00007fff2fdbd203 (in AE)
32 0x00007fff2fdbc929 (in AE)
33 aeProcessAppleEvent (in AE)
34 AEProcessAppleEvent (in HIToolbox)
35 DPSNextEvent (in AppKit)
36 -[NSApplication(NSEvent) nextEventMatchingEventMask:untilDate:inMode:dequeue:] (in AppKit)
37 -[DVTApplication nextEventMatchingMask:untilDate:inMode:dequeue:] (in DVTKit)
38 -[NSApplication run] (in AppKit)
39 NSApplicationMain (in AppKit)
40 start (in libdyld.dylib)

abort() called