proresdec: support mixed interlaced/non-interlaced content

Set interlaced to false if we don't have an interlaced frame
Signed-off-by: Luca Barbato <lu_zero@gentoo.org>

libavcodec/proresdec.c

@@ -164,6 +164,8 @@ static int decode_frame_header(ProresContext *ctx, const uint8_t *buf,
     if (ctx->frame_type) {      /* if interlaced */
         ctx->picture.interlaced_frame = 1;
         ctx->picture.top_field_first  = ctx->frame_type & 1;
+    } else {
+        ctx->picture.interlaced_frame = 0;
     }
 
     avctx->color_primaries = buf[14];