Fix warning about missing initializer for a struct member

GCC 4.8 is complaining about perfectly valid (and recommended) code but
we still support it, so...

qcborvalue.h:74:25: warning: missing initializer for member ‘QCborError::c’

Fixes: QTBUG-71222
Change-Id: If7e743cf8476463880ccfffd155e8775b6b95469
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>

src/corelib/serialization/qcborvalue.h

@@ -71,7 +71,7 @@ class QCborStreamWriter;
 struct QCborParserError
 {
     qint64 offset = 0;
-    QCborError error = {};
+    QCborError error = { QCborError::NoError };
 
     QString errorString() const { return error.toString(); }
 };