avformat/vividas: Fix invalid shift in decode_key()

Fixes: left shift of 1 by 31 places cannot be represented in type 'int'
Fixes: 15118/clusterfuzz-testcase-minimized-ffmpeg_DEMUXER_fuzzer-5740230004441088

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/vividas.c

@@ -91,7 +91,7 @@ static uint32_t decode_key(uint8_t *buf)
 
     for (int i = 0; i < 32; i++) {
         unsigned p = keybits[i];
-        key |= !!(buf[p>>3] & (1<<(p&7))) << i;
+        key |= (unsigned)!!(buf[p>>3] & (1<<(p&7))) << i;
     }
 
     return key;