M3UParser: handle missing EXT-X-MEDIA URIs

Bug: 111381540
Test: http://devimages.apple.com.edgekey.net/streaming/examples/bipbop_16x9/bipbop_16x9_variant.m3u8
Change-Id: I57f6cea59ce4c25267385289ab805eefe74b04ac
(cherry picked from commit b8c3a74de55a76e2ee21c731828a8afca7aa4ae0)
1 file changed