launcher: Throw error if no data files are selected

apps/launcher/maindialog.cpp

@@ -531,6 +531,17 @@ bool MainDialog::writeSettings()
         }
     }
 
+    if(!mGameSettings.hasMaster()) {
+            QMessageBox msgBox;
+            msgBox.setWindowTitle(tr("Error writing OpenMW configuration file"));
+            msgBox.setIcon(QMessageBox::Critical);
+            msgBox.setStandardButtons(QMessageBox::Ok);
+            msgBox.setText(tr("<br><b>You do not have any master files selected.</b><br><br> \
+                              Please select one and try again.<br>"));
+            msgBox.exec();
+            return false;
+    }
+
     // Game settings
     QFile file(userPath + QString("openmw.cfg"));
 

apps/launcher/settings/gamesettings.hpp

@@ -43,6 +43,7 @@ public:
     inline QStringList getDataDirs() { return mDataDirs; }
     inline void addDataDir(const QString &dir) { if(!dir.isEmpty()) mDataDirs.append(dir); }
     inline QString getDataLocal() {return mDataLocal; }
+    inline bool hasMaster() { return mSettings.count(QString("master")) > 0; }
 
     QStringList values(const QString &key, const QStringList &defaultValues = QStringList());
     bool readFile(QTextStream &stream);