+ split file extension from descriptive text of file format to avoid that invalid translation breaks file dialog

+ add method to make image view unclosable for user
+ fix possible crash in MeshAlgorithm::GetMeshBorder
+ fix possible crash in MeshAlgorithm::ConnectLines

src/Gui/Document.cpp

@@ -629,7 +629,7 @@ bool Document::saveAs(void)
 
     QString exe = qApp->applicationName();
     QString fn = FileDialog::getSaveFileName(getMainWindow(), QObject::tr("Save %1 Document").arg(exe), 
-                                             QString(), QObject::tr("%1 document (*.FCStd)").arg(exe));
+        QString(), QString::fromLatin1("%1 %2 (*.FCStd)").arg(exe).arg(QObject::tr("Document")));
     if (!fn.isEmpty()) {
         QFileInfo fi;
         fi.setFile(fn);