nutdec: fix integer overflow

Fixes CID700575
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/nutdec.c

@@ -789,7 +789,7 @@ static int decode_frame_header(NUTContext *nut, int64_t *pts, int *stream_id,
         if (coded_pts < (1 << stc->msb_pts_shift)) {
             *pts = ff_lsb2full(stc, coded_pts);
         } else
-            *pts = coded_pts - (1 << stc->msb_pts_shift);
+            *pts = coded_pts - (1LL << stc->msb_pts_shift);
     } else
         *pts = stc->last_pts + pts_delta;
     if (flags & FLAG_SIZE_MSB)