add load button to non-ideal state in the image viewer widget and the catalog widget

[kswang1029]

This is a user request.

The idea is to add a shortcut button for the file browser in the image and catalog widgets when it is in the non-ideal state.
Like the following screenshots, the idea is to add a shortcut in the image viewer widget when there is no image loaded or add a shortcut in the catalog widget when there is image loaded but no catalog is loaded.