ParameterEditorDialog: set focus to the text field when changing parameters

src/QmlControls/ParameterEditorDialog.qml

@@ -85,6 +85,11 @@ QGCViewDialog {
         }
     }
 
+	// set focus to the text field when becoming visible (in case of an Enum,
+	// the valueField is not visible, but it's not an issue because the combo
+	// box cannot have a focus)
+	onVisibleChanged: if (visible) valueField.forceActiveFocus()
+
     QGCFlickable {
         anchors.fill:       parent
         contentHeight:      _column.y + _column.height