avfilter/vf_removelogo: use av_freep() for saftey

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

libavfilter/vf_removelogo.c

@@ -235,8 +235,8 @@ static int load_mask(uint8_t **mask, int *w, int *h,
     av_image_copy_plane(*mask, *w, gray_data[0], gray_linesize[0], *w, *h);
 
 end:
-    av_free(src_data[0]);
-    av_free(gray_data[0]);
+    av_freep(&src_data[0]);
+    av_freep(&gray_data[0]);
     return ret;
 }
 
@@ -540,9 +540,9 @@ static av_cold void uninit(AVFilterContext *ctx)
         for (a = 0; a <= s->max_mask_size; a++) {
             /* Loop through each scanline in a mask. */
             for (b = -a; b <= a; b++) {
-                av_free(s->mask[a][b + a]); /* Free a scanline. */
+                av_freep(&s->mask[a][b + a]); /* Free a scanline. */
             }
-            av_free(s->mask[a]);
+            av_freep(&s->mask[a]);
         }
         /* Free the array of pointers pointing to the masks. */
         av_freep(&s->mask);