avcodec/h264_slice: Remove dead sps check

Fixes: CID1439574 Dereference after null check

Sponsored-by: Sovereign Tech Fund
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit a68aa951b2)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/h264_slice.c

@@ -1398,7 +1398,7 @@ static int h264_field_start(H264Context *h, const H264SliceContext *sl,
 
     sps = h->ps.sps;
 
-    if (sps && sps->bitstream_restriction_flag &&
+    if (sps->bitstream_restriction_flag &&
         h->avctx->has_b_frames < sps->num_reorder_frames) {
         h->avctx->has_b_frames = sps->num_reorder_frames;
     }