lavc/qsvenc: replace assert with error return

Fix the (m)jpeg encoding regression issue as decription in tikect #7593,
due to bs->FrameType is not set in such case in
MSDK (https://github.com/Intel-Media-SDK/MediaSDK/issues/970).
(And assert on a value coming from an external library is not proper.)

Add default type check for bs->FrameType, and return invalid data error in function
ff_qsv_encode to avoid using uninitialized value.
Signed-off-by: Linjie Fu <linjie.fu@intel.com>
Signed-off-by: Zhong Li <zhong.li@intel.com>

libavcodec/qsvenc.c

@@ -1344,8 +1344,13 @@ int ff_qsv_encode(AVCodecContext *avctx, QSVEncContext *q,
             pict_type = AV_PICTURE_TYPE_P;
         else if (bs->FrameType & MFX_FRAMETYPE_B || bs->FrameType & MFX_FRAMETYPE_xB)
             pict_type = AV_PICTURE_TYPE_B;
-        else
-            av_assert0(!"Uninitialized pict_type!");
+        else if (bs->FrameType == MFX_FRAMETYPE_UNKNOWN) {
+            pict_type = AV_PICTURE_TYPE_NONE;
+            av_log(avctx, AV_LOG_WARNING, "Unkown FrameType, set pict_type to AV_PICTURE_TYPE_NONE.\n");
+        } else {
+            av_log(avctx, AV_LOG_ERROR, "Invalid FrameType:%d.\n", bs->FrameType);
+            return AVERROR_INVALIDDATA;
+        }
 
 #if FF_API_CODED_FRAME
 FF_DISABLE_DEPRECATION_WARNINGS