Spin box: fix input of double values in locales with non-point decima…

…l separator

src/core/expression/qgsexpression.cpp

@@ -471,7 +471,9 @@ double QgsExpression::evaluateToDouble( const QString &text, const double fallba
 {
   bool ok;
   //first test if text is directly convertible to double
-  double convertedValue = text.toDouble( &ok );
+  // use system locale: e.g. in German locale, user is presented with numbers "1,23" instead of "1.23" in C locale
+  // so we also want to allow user to rewrite it to "5,23" and it is still accepted
+  double convertedValue = QLocale::system().toDouble( text, &ok );
   if ( ok )
   {
     return convertedValue;