HLS: Do not assume Content-Length is set
HLS: Do not assume Content-Length is set

Fixes #8078

(cherry picked from commit b48ee570b0e060d64dec95d460ca919d60d06138)
Signed-off-by: Felix Paul Kühne <af44a38b4065def9b90f0b66e4658837dd45b77d@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