macosx: fix crash occuring while initializing the info panel
macosx: fix crash occuring while initializing the info panel

It is not allowed to call [[VLCMain sharedInstance] info]
on the non-main-thread, as this might load and initialize the
info window.

(cherry picked from commit d87928927015fad3cdbcd0309bf3185c3672822f)
Signed-off-by: David Fuhrmann <0373137a05c54ad8db3bae67bf852110dab006a2@videolan.org>

jomanmuk/vlc-2.2,jomanmuk/vlc-2.2,jomanmuk/vlc-2.2,jomanmuk/vlc-2.2,jomanmuk/vlc-2.2,jomanmuk/vlc-2.2,jomanmuk/vlc-2.2