Core::Id: Do not warn when reading invalid ids from settings

Change-Id: Ic2fc0df7f3ac5e8006123bf94c4e55a3a7d86593
Reviewed-by: hjk <hjk121@nokiamail.com>

src/plugins/coreplugin/id.cpp

@@ -254,6 +254,8 @@ QVariant Id::toSetting() const
 Id Id::fromSetting(const QVariant &variant)
 {
     const QByteArray ba = variant.toString().toUtf8();
+    if (ba.isEmpty())
+        return Id();
     return Id(theId(ba));
 }