Bugfix: guard NPE in ApiError creation.

src/buffoonery/apierror.nim

@@ -10,7 +10,9 @@ proc newApiError*(parent: ref Exception = nil, respCode: HttpCode, respMsg: stri
   result = newException(ApiError, msg, parent)
   result.respCode = respCode
   result.respMsg = respMsg
-  result.trace &= parent.trace
+
+  if not parent.isNil:
+    result.trace &= parent.trace
 
 
 proc raiseApiError*(respCode: HttpCode, respMsg: string, msg = "") =