Fix mount dropdown

src/components/MountItem/MountItem.js

@@ -67,13 +67,14 @@ export default connect(mapStateToProps, mapDispatchToProps)(props => {
   let inputControls = null;
   if (props.Platform === 'win32') {
     inputColumnSpan = 20;
+    const index = props.MState.DriveLetters.indexOf(props.PState.MountLocation);
     inputControls = <DropDown changed={props.changed}
                               colSpan={inputColumnSpan}
                               disabled={!props.MState.AllowMount || props.MState.Mounted}
                               items={props.MState.DriveLetters}
                               row={secondRow}
                               rowSpan={7}
-                              selected={props.MState.DriveLetters.indexOf(props.PState.MountLocation)}/>;
+                              selected={index >= 0 ? props.PState.MountLocation : ''}/>;
 
   } else {
     inputColumnSpan = 64;