ffv1: fix reading global header with CRC

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit 21fdf1ccf0)

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/ffv1.c

@@ -1697,8 +1697,10 @@ static int read_extra_header(FFV1Context *f){
     ff_build_rac_states(c, 0.05*(1LL<<32), 256-8);
 
     f->version= get_symbol(c, state, 0);
-    if(f->version > 2)
+    if(f->version > 2) {
+        c->bytestream_end -= 4;
         f->minor_version= get_symbol(c, state, 0);
+    }
     f->ac= f->avctx->coder_type= get_symbol(c, state, 0);
     if(f->ac>1){
         for(i=1; i<256; i++){