App crashes on launch

[AngeloStavrow]

This seems to happen mainly on iPhone when launching to a new local post, but I've also seen this happen when tapping the reload-from-server button; the app crashes with the following stack trace:

2020-11-02 15:09:44.233200-0500 WriteFreely-MultiPlatform[53569:8780093] [] nw_protocol_get_quic_image_block_invoke dlopen libquic failed
2020-11-02 15:09:46.202943-0500 WriteFreely-MultiPlatform[53569:8779747] *** Terminating app due to uncaught exception 'NSGenericException', reason: '*** Collection <__NSCFSet: 0x600002830cf0> was mutated while being enumerated.'
*** First throw call stack:
(
	0   CoreFoundation                      0x00007fff2043a126 __exceptionPreprocess + 242
	1   libobjc.A.dylib                     0x00007fff20177f78 objc_exception_throw + 48
	2   CoreFoundation                      0x00007fff2043968d +[__NSFastEnumerationEnumerator allocWithZone:] + 0
	3   CoreData                            0x00007fff250e8ef8 -[NSManagedObjectContext executeFetchRequest:error:] + 2219
	4   CoreData                            0x00007fff252a8939 __43-[NSFetchedResultsController performFetch:]_block_invoke + 417
	5   CoreData                            0x00007fff2511d933 developerSubmittedBlockToNSManagedObjectContextPerform + 154
	6   CoreData                            0x00007fff2511d81a -[NSManagedObjectContext performBlockAndWait:] + 197
	7   CoreData                            0x00007fff252aadcc -[NSFetchedResultsController _recursivePerformBlockAndWait:withContext:] + 145
	8   CoreData                            0x00007fff252a868c -[NSFetchedResultsController performFetch:] + 231
	9   SwiftUI                             0x00007fff563da9de $s7SwiftUI12FetchRequestV6updateyyF + 1790
	10  SwiftUI                             0x00007fff560da4e8 $s7SwiftUI26EmbeddedDynamicPropertyBox33_49D2A32E637CD497C6DE29B8E060A506LLV6update8property5phaseSbxz_AA12_GraphInputsV5PhaseVtF + 24
	11  SwiftUI                             0x00007fff5641bd6c $s7SwiftUI9BoxVTable33_68550FF604D39F05971FE35A26EE75B0LLC6update3ptr8property5phaseSbSv_SvAA12_GraphInputsV5PhaseVtFZ + 204
	12  SwiftUI                             0x00007fff5641b49e $s7SwiftUI22_DynamicPropertyBufferV6update9container5phaseSbSv_AA12_GraphInputsV5PhaseVtF + 110
	13  SwiftUI                             0x00007fff560db230 $s7SwiftUI11DynamicBodyV11updateValueyyF + 512
	14  SwiftUI                             0x00007fff55df081a $s14AttributeGraph0A0VyACyxGqd__c5ValueQyd__RszAA12StatefulRuleRd__lufcADSPyqd__GXEfU_ySv_So11AGAttributeatcyXEfU_ySv_AJtcqd__mcfu_ySv_AJtcfu0_TA + 26
	15  AttributeGraph                      0x00007fff4ba16d03 _ZN2AG5Graph11UpdateStack6updateEv + 505
	16  AttributeGraph                      0x00007fff4ba17199 _ZN2AG5Graph16update_attributeENS_4data3ptrINS_4NodeEEEb + 335
	17  AttributeGraph                      0x00007fff4ba1f245 _ZN2AG8Subgraph6updateEj + 781
	18  SwiftUI                             0x00007fff56407baa $s7SwiftUI9GraphHostC14runTransactionyyF + 186
	19  SwiftUI                             0x00007fff5640b6bf $s7SwiftUI9GraphHostC14runTransaction33_30C09FF16BC95EC5173809B57186CAC3LLyyAA05AsyncF0AELLCF + 79
	20  SwiftUI                             0x00007fff5640a1e3 $s7SwiftUI9GraphHostC17flushTransactionsyyF + 211
	21  SwiftUI                             0x00007fff5640b65f $s7SwiftUI9GraphHostC16asyncTransaction_8mutation5styleyAA0F0V_xAA01_C14Mutation_StyleOtAA0cI0RzlFyycfU_yACXEfU_ + 15
	22  SwiftUI                             0x00007fff5640ab49 $s7SwiftUI9GraphHostCIgg_ACytIeggr_TR03$s7a3UI9cD92C16asyncTransaction_8mutation5styleyAA0F0V_xAA01_C14Mutation_StyleOtAA0cI0RzlFyycfU_yACXEfU_Tf3nnpf_n + 9
	23  SwiftUI                             0x00007fff55ef7091 $s7SwiftUI17ViewGraphDelegatePAAE06updateD04bodyqd__qd__AA0D4HostCXE_tlFqd__AA0cD0CXEfU_TA + 17
	24  SwiftUI                             0x00007fff5636dada $s7SwiftUI16ViewRendererHostPAAE06updateC5Graph4bodyqd__qd__AA0cG0CXE_tlFqd__yXEfU_ + 74
	25  SwiftUI                             0x00007fff56361319 $s7SwiftUI16ViewRendererHostPAAE06updateC5Graph4bodyqd__qd__AA0cG0CXE_tlF + 73
	26  SwiftUI                             0x00007fff563611a9 $s7SwiftUI14_UIHostingViewCyqd__GAA0D13GraphDelegateA2aEP06updatedE04bodyqd__qd__AA0dE0CXE_tlFTW + 25
	27  SwiftUI                             0x00007fff55ef3237 $s7SwiftUI17ViewGraphDelegatePAAE06updateD04bodyqd__qd__AA0D4HostCXE_tlF + 55
	28  SwiftUI                             0x00007fff55ef31f9 $s7SwiftUI14_UIHostingViewCyqd__GAA13GraphDelegateA2aEP06updateE04bodyqd__qd__AA0E4HostCXE_tlFTW + 25
	29  SwiftUI                             0x00007fff5640b63a $s7SwiftUI9GraphHostC4dataA2C4DataV_tcfcyycfU_Tm + 122
	30  SwiftUI                             0x00007fff5640cce3 $s7SwiftUI9GraphHostC16asyncTransaction_8mutation5styleyAA0F0V_xAA01_C14Mutation_StyleOtAA0cI0RzlFyycfU_TA.11 + 19
	31  SwiftUI                             0x00007fff55f13d0c $sIeg_ytIegr_TR + 12
	32  SwiftUI                             0x00007fff55c31011 $sIeg_ytIegr_TRTA + 17
	33  SwiftUI                             0x00007fff55c30eb3 $sSo9NSRunLoopC7SwiftUIE14flushObserversyyFZ + 115
	34  SwiftUI                             0x00007fff55c30e39 $sSo9NSRunLoopC7SwiftUIE11addObserveryyyycFZySo05CFRunbF3RefaSg_So0gB8ActivityVSvSgtcfU_yyXEfU_ + 9
	35  SwiftUI                             0x00007fff55c2b35e $ss5Error_pIgzo_ytsAA_pIegrzo_TR95$sSo9NSRunLoopC7SwiftUIE11addObserveryyyycFZySo05CFRunbF3RefaSg_So0gB8ActivityVSvSgtcfU_yyXEfU_Tf3npf_n + 14
	36  libswiftObjectiveC.dylib            0x00007fff53c04f8e $s10ObjectiveC15autoreleasepool8invokingxxyKXE_tKlF + 46
	37  SwiftUI                             0x00007fff55c30e23 $sSo9NSRunLoopC7SwiftUIE11addObserveryyyycFZySo05CFRunbF3RefaSg_So0gB8ActivityVSvSgtcfU_ + 35
	38  SwiftUI                             0x00007fff55c30f2b $sSo9NSRunLoopC7SwiftUIE11addObserveryyyycFZySo05CFRunbF3RefaSg_So0gB8ActivityVSvSgtcfU_To + 43
	39  CoreFoundation                      0x00007fff203a76b3 __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 23
	40  CoreFoundation                      0x00007fff203a1f3f __CFRunLoopDoObservers + 547
	41  CoreFoundation                      0x00007fff203a24e2 __CFRunLoopRun + 1113
	42  CoreFoundation                      0x00007fff203a1b9e CFRunLoopRunSpecific + 567
	43  GraphicsServices                    0x00007fff2b793db3 GSEventRunModal + 139
	44  UIKitCore                           0x00007fff2466d40f -[UIApplication _run] + 912
	45  UIKitCore                           0x00007fff24672320 UIApplicationMain + 101
	46  SwiftUI                             0x00007fff5639fdf7 $s7SwiftUI17KitRendererCommon33_ACC2C5639A7D76F611E170E831FCA491LLys5NeverOyXlXpFAESpySpys4Int8VGSgGXEfU_ + 119
	47  SwiftUI                             0x00007fff5639fd6f $s7SwiftUI6runAppys5NeverOxAA0D0RzlF + 143
	48  SwiftUI                             0x00007fff55eeee5d $s7SwiftUI3AppPAAE4mainyyFZ + 61
	49  WriteFreely-MultiPlatform           0x000000010882c711 $s25WriteFreely_MultiPlatform0ab1_cD3AppV5$mainyyFZ + 33
	50  WriteFreely-MultiPlatform           0x000000010882c7c4 main + 20
	51  libdyld.dylib                       0x00007fff20257409 start + 1
	52  ???                                 0x0000000000000001 0x0 + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException
*** Terminating app due to uncaught exception 'NSGenericException', reason: '*** Collection <__NSCFSet: 0x600002830cf0> was mutated while being enumerated.'
terminating with uncaught exception of type NSException
CoreSimulator 732.18.0.2 - Device: iPhone 12 Pro Max (D6B75BB9-C1A7-49AD-916B-EBACFE8D5C24) - Runtime: iOS 14.1 (18A8394) - DeviceType: iPhone 12 Pro Max