Small interface cleanup in ctkDICOMDatabase

Libs/DICOM/Core/ctkDICOMDatabase.cpp

@@ -137,7 +137,7 @@ ctkDICOMDatabase::~ctkDICOMDatabase()
 //----------------------------------------------------------------------------
 
 //------------------------------------------------------------------------------
-const QString& ctkDICOMDatabase::GetLastError() const {
+const QString ctkDICOMDatabase::GetLastError() const {
   Q_D(const ctkDICOMDatabase);
   return d->LastError;
 }

Libs/DICOM/Core/ctkDICOMDatabase.h

@@ -39,7 +39,7 @@ public:
   virtual ~ctkDICOMDatabase();
 
   const QSqlDatabase& database() const;
-  const QString& GetLastError() const;
+  const QString GetLastError() const;
 
   ///
   /// open the SQLite database in @param file. If the file does not