Fix MovieDetails crash

[cewert]

Validate item.json before using to prevent crash. This comes from the roku crash log.

Crashlog:

'Dot' Operator attempted with invalid BrightScript Component or interface reference. (runtime error &hec) in pkg:/components/movies/MovieDetails.brs(97) 
Backtrace: 
#0  Function itemcontentchanged() As Voi$1 file/line: pkg:/components/movies/MovieDetails.brs(97) 
Local Variables: 
global           Interface:ifGloba$1 m                roAssociativeArray refcnt=2 count:14 
item             roSGNode:MovieData refcnt=1 
itemdata         Invali$1 tomato           <uninitialized> 
directors        <uninitialized> 
person           <uninitialized> 
airdate          <uninitialized>

which points to this line after running build-prod on 2.1.2:

m.top.id = itemData.id

Issues

Ref #1164

[jellyfin-bot]

This pull request has merge conflicts. Please resolve the conflicts so the PR can be reviewed. Thanks!