avfilter: Read errno before av_log() as the callback from av_log() might affect errno

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

libavfilter/vf_vidstabdetect.c

@@ -176,8 +176,9 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *in)
         return AVERROR(AVERROR_EXTERNAL);
     } else {
         if (vsWriteToFile(md, sd->f, &localmotions) != VS_OK) {
+            int ret = AVERROR(errno);
             av_log(ctx, AV_LOG_ERROR, "cannot write to transform file");
-            return AVERROR(errno);
+            return ret;
         }
         vs_vector_del(&localmotions);
     }

libavfilter/vf_vidstabtransform.c

@@ -208,8 +208,9 @@ static int config_input(AVFilterLink *inlink)
 
     f = fopen(tc->input, "r");
     if (!f) {
+        int ret = AVERROR(errno);
         av_log(ctx, AV_LOG_ERROR, "cannot open input file %s\n", tc->input);
-        return AVERROR(errno);
+        return ret;
     } else {
         VSManyLocalMotions mlms;
         if (vsReadLocalMotionsFile(f, &mlms) == VS_OK) {