vf_psnr/ssim: don't crash if stats_file is NULL.

libavfilter/vf_psnr.c

@@ -193,9 +193,10 @@ static av_cold int init(AVFilterContext *ctx)
     s->min_mse = +INFINITY;
     s->max_mse = -INFINITY;
 
+    if (s->stats_file_str) {
         if (!strcmp(s->stats_file_str, "-")) {
             s->stats_file = stdout;
-    } else if (s->stats_file_str) {
+        } else {
             s->stats_file = fopen(s->stats_file_str, "w");
             if (!s->stats_file) {
                 int err = AVERROR(errno);
@@ -206,6 +207,7 @@ static av_cold int init(AVFilterContext *ctx)
                 return err;
             }
         }
+    }
 
     s->dinput.process = do_psnr;
     return 0;

libavfilter/vf_ssim.c

@@ -223,9 +223,10 @@ static av_cold int init(AVFilterContext *ctx)
 {
     SSIMContext *s = ctx->priv;
 
+    if (s->stats_file_str) {
         if (!strcmp(s->stats_file_str, "-")) {
             s->stats_file = stdout;
-    } else if (s->stats_file_str) {
+        } else {
             s->stats_file = fopen(s->stats_file_str, "w");
             if (!s->stats_file) {
                 int err = AVERROR(errno);
@@ -236,6 +237,7 @@ static av_cold int init(AVFilterContext *ctx)
                 return err;
             }
         }
+    }
 
     s->dinput.process = do_ssim;
     s->dinput.shortest = 1;