[video] fix "Browse" button in CGUIDialogVideoInfo for tvshows

[Montellese]

Description

In my media import work I got a report that the "Browse" button in the video info dialog is not working for imported tvshows. This fixes the issue. The same issue can currently happen if a user sets up a tvshow using NFOs which cannot be looked up using a scraper. I'm guessing this code exists since before we explicitely tag media items with their type.

On a side note I noticed that the "Browse" button is very confusing when the user opens the video info dialog on a tvshow season because he actually ends up in the video info dialog for the tvshow and not the season. So using the "Browse" button there brings you back to the list of seasons and not to the list of episodes of the selected season.

Types of change

• Bug fix (non-breaking change which fixes an issue)
• Clean up (non-breaking change which removes non-working, unmaintained functionality)
• Improvement (non-breaking change which improves existing functionality)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that will cause existing functionality to change)
• Cosmetic change (non-breaking change that doesn't touch code)
• None of the above (please explain below)

Checklist:

• My code follows the Code Guidelines of this project
• My change requires a change to the documentation, either Doxygen or wiki
• I have updated the documentation accordingly
• I have read the Contributing document
• I have added tests to cover my change
• All new and existing tests passed