avfilter/vf_colormatrix: fix memleak on error

Fixes CID1197065
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavfilter/vf_colormatrix.c

@@ -353,6 +353,7 @@ static int filter_frame(AVFilterLink *link, AVFrame *in)
         case AVCOL_SPC_BT470BG   : source = COLOR_MODE_BT601     ; break;
         default :
             av_log(ctx, AV_LOG_ERROR, "Input frame does not specify a supported colorspace, and none has been specified as source either\n");
+            av_frame_free(&out);
             return AVERROR(EINVAL);
         }
         color->mode = source * 4 + color->dest;