QmlJS: Don't parse files we cannot open

This rids us of the "Issues" about various wizard files when opening
qtcreator.pro

Change-Id: Ib49e87ded791bcc9155e65a77cac523c1f67de56
Reviewed-by: Marco Benelli <marco.benelli@qt.io>

src/libs/qmljs/qmljsmodelmanagerinterface.cpp

@@ -888,6 +888,8 @@ void ModelManagerInterface::parseLoop(QSet<QString> &scannedPaths,
                 QTextStream ins(&inFile);
                 contents = ins.readAll();
                 inFile.close();
+            } else {
+                continue;
             }
         }