Prevent crash when video path is invalid

[cewert]

Don't send invalid to isLocalHost()

Comes from roku.com crash log:

   file/line: pkg:/components/ItemGrid/LoadVideoContentTask.brs(190) 
m                roAssociativeArray refcnt=6 count:3 
#2  Function loaditems_addvideocontent(video As Object, mediasourceid As Dynamic, audio_stream_idx As Integer, forcetranscoding As Boolean) As Voi$1 file/line: pkg:/components/ItemGrid/LoadVideoContentTask.brs(322) 
#3  Function addvideocontenturl(video As Dynamic, mediasourceid As Dynamic, audio_stream_idx As Dynamic, fully_external As Dynamic) As Voi$1 file/line: pkg:/source/utils/misc.brs(389) 
#4  Function islocalhost(url As String) As Boolea$1 Backtrace: 
Type Mismatch. Unable to cast "Invalid" to "String". (runtime error &h18) in pkg:/source/utils/misc.brs(387) 
   file/line: pkg:/components/ItemGrid/LoadVideoContentTask.brs(54) 
   file/line: pkg:/components/ItemGrid/LoadVideoContentTask.brs(46) 
Local Variables: 
#0  Function loaditems() As Voi$1 global           Interface:ifGloba$1 url              Invalid

which points to this line after running build-prod on 2.1.4:

function isLocalhost(url as string) as boolean

Issues

Ref #1164