dshow: fix timestamp conversion (fixes #11725)
dshow: fix timestamp conversion (fixes #11725)

Zero is a legal REFERENCE_TIME value.

(cherry picked from commit dddf319b0bd8b7d04881497f18aab57b04ae437c)
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