i cant open my uiview kit any time i load it up shows white [duplicate]

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• What does this mean? “'NSUnknownKeyException', reason: … this class is not key value coding-compliant for the key X” 64 answers

2018-03-07 18:50:49.374014-0600 swift saver[10694:4163485] [Accessibility] ****************** Loading GAX Client Bundle **************** 2018-03-07 18:50:50.312532-0600 swift saver[10694:4163485] [MC] Lazy loading NSBundle MobileCoreServices.framework 2018-03-07 18:50:50.313314-0600 swift saver[10694:4163485] [MC] Loaded MobileCoreServices.framework 2018-03-07 18:50:50.323229-0600 swift saver[10694:4163485] * Terminating app due to uncaught exception 'NSUnknownKeyException', reason: '[ setValue:forUndefinedKey:]: this class is not key value coding-compliant for the key backButtontap.' * First throw call stack: (0x183a07164 0x182c50528 0x183a06e2c 0x18431e630 0x18d32d134 0x18d555224 0x183913d14 0x18d553c18 0x18d330be0 0x18d0de8e8 0x18cfc16a8 0x18cfc15d8 0x18cfc81a4 0x18cfc5404 0x18d0342e8 0x18d221c7c 0x18d226a14 0x18d4c22a8 0x18d79a100 0x18d4c1f0c 0x18d4c276c 0x18dc477c0 0x18dc47664 0x18d9b52cc 0x18db4e3cc 0x18d9b517c 0x18d799760 0x18d225158 0x18d63adbc 0x1860ca1f0 0x1860d2af8 0x101a6d28c 0x101a799e4 0x1860fe7f8 0x1860fe49c 0x1860fea38 0x1839af77c 0x1839af6fc 0x1839aef84 0x1839acb5c 0x1838ccc58 0x185778f84 0x18d0255c4 0x100c7d470 0x1833ec56c) libc++abi.dylib: terminating with uncaught exception of type NSException (lldb)