Fix GridItem crash

[cewert]

This appears to be another one of those weird roku bugs since m.global.session.user.settings should always be valid after the user logs in. Instead of accessing and validating m.global and m.global.session etc for every single item in the grid, I'm accessing the user setting from global once and saving it to a field on ItemGrid. Even with roku weirdness I believe we will always have access to the parent node and hopefully this way we can avoid adding a bunch of validation for every single item in the grid.

Comes from roku.com crash log:

m                roAssociativeArray refcnt=2 count:13 
'Dot' Operator attempted with invalid BrightScript Component or interface reference. (runtime error &hec) in pkg:/components/ItemGrid/GridItem.brs(24) 
Backtrace: 
#0  Function init() As Voi$1 file/line: pkg:/components/ItemGrid/GridItem.brs(24) 
Local Variables: 
global           Interface:ifGlobal

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

m.gridTitles = m.global.session.user.settings["itemgrid.gridTitles"]

Issues

Ref #1164

[jimdogx]

This will probably have some conflicts when merging to Master since this file was just updated recently. Hopefully not too bad though.