Improve checks for runt video packets

Since we always allocate fixed size these aren't likely to be exploitable,
but we ought to fix them anyway. Worst case, we will just read some garbage
and generate corrupt video output.

src/RtpVideoQueue.c

@@ -539,6 +539,11 @@ int RtpvAddPacket(PRTP_VIDEO_QUEUE queue, PRTP_PACKET packet, int length, PRTPV_
         dataOffset += 4; // 2 additional fields
     }
 
+    if (length < dataOffset + (int)sizeof(NV_VIDEO_PACKET)) {
+        // Reject packets that are too small to fit a NV_VIDEO_PACKET header
+        return RTPF_RET_REJECTED;
+    }
+
     PNV_VIDEO_PACKET nvPacket = (PNV_VIDEO_PACKET)(((char*)packet) + dataOffset);
 
     nvPacket->streamPacketIndex = LE32(nvPacket->streamPacketIndex);