Fix MovieDetails crash (2)

[cewert]

Validate criticRatingIcon node exists before using to prevent crash. This comes from the roku crash log.

Crashlog:

Invalid value for left-side of expression. (runtime error &he4) in pkg:/components/movies/MovieDetails.brs(127) 
Backtrace: 
#0  Function itemcontentchanged() As Voi$1 file/line: pkg:/components/movies/MovieDetails.brs(128) 
Local Variables: 
global           Interface:ifGloba$1 m                roAssociativeArray refcnt=2 count:14 
item             roSGNode:MovieData refcnt=1 
itemdata         roAssociativeArray refcnt=1 count:53 
tomato           String (VT_STR_CONST) val:"pkg:/images/fresh.png" 
directors        <uninitialized> 
person           <uninitialized> 
airdate          <uninitialized>

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

m.top.findNode("criticRatingIcon").uri = tomato

Issues

Ref #1164