android opaque: check error when locking the subtitles surface
android opaque: check error when locking the subtitles surface

(cherry picked from commit 2da3279c1765294d19980b0539d7fe7433942b8d)
Signed-off-by: Jean-Baptiste Kempf <7b85a41a628204b76aba4326273a3ccc74bd009a@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