libvlc: fix vbi-page initialization without zvbi plugin
libvlc: fix vbi-page initialization without zvbi plugin

A variable cannot be inherited if it is not a configuration item.
Note this only avoids generating an error; VBI cannot work without the
plugin anyway.

xkfz007/vlc,krichter722/vlc,krichter722/vlc,xkfz007/vlc,vlc-mirror/vlc,shyamalschandra/vlc,vlc-mirror/vlc,vlc-mirror/vlc,krichter722/vlc,shyamalschandra/vlc,shyamalschandra/vlc,xkfz007/vlc,krichter722/vlc,vlc-mirror/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,shyamalschandra/vlc,shyamalschandra/vlc,shyamalschandra/vlc,krichter722/vlc,vlc-mirror/vlc,vlc-mirror/vlc,vlc-mirror/vlc,krichter722/vlc,krichter722/vlc,shyamalschandra/vlc