C++: Exclude error types from WrongTypeFormatArguments.

Author: geoffw0

cpp/ql/src/Likely Bugs/Format/WrongTypeFormatArguments.ql

@@ -155,7 +155,8 @@ where
     not actual.getUnspecifiedType().(IntegralType).getSize() = sizeof_IntType()
   ) and
   not arg.isAffectedByMacro() and
-  not arg.isFromUninstantiatedTemplate(_)
+  not arg.isFromUninstantiatedTemplate(_) and
+  not actual.getUnspecifiedType() instanceof ErroneousType
 select arg,
   "This argument should be of type '" + expected.getName() + "' but is of type '" +
     actual.getUnspecifiedType().getName() + "'"