Fix infinite spinner bugs

[cewert]

In loadMoreData(), only show the spinner when m.Loading is false.

Changes

• Fix lazy loading itemgrid spinner bug

[1hitsong]

Found another path to an infinite spinner. In a library click a letter or scroll down until a spinner shows. Press the back button while it's spinning. You end up on the previous view with the spinner still going.

[cewert]

I added a stopLoadingSpinner() call to the end of scenemangers popScene() function and that fixes the issue. popScene() gets called when we hit back to navigate to a previous screen in the stack. If the previous screen shows a loading spinner the spinner may flicker but I don't think there is an example of that in our app at the moment.