avformat/segment: Use av_freep() avoid leaving stale pointers in memory

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit 68fa5492)
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/segment.c

@@ -343,7 +343,7 @@ static int segment_end(AVFormatContext *s, int write_trailer, int is_last)
             if (seg->list_size && seg->segment_count >= seg->list_size) {
                 entry = seg->segment_list_entries;
                 seg->segment_list_entries = seg->segment_list_entries->next;
-                av_free(entry->filename);
+                av_freep(&entry->filename);
                 av_freep(&entry);
             }
 
@@ -501,10 +501,10 @@ static int open_null_ctx(AVIOContext **ctx)
     return 0;
 }
 
-static void close_null_ctx(AVIOContext *pb)
+static void close_null_ctxp(AVIOContext **pb)
 {
-    av_free(pb->buffer);
-    av_free(pb);
+    av_freep(&(*pb)->buffer);
+    av_freep(pb);
 }
 
 static int select_reference_stream(AVFormatContext *s)
@@ -687,7 +687,7 @@ static int seg_write_header(AVFormatContext *s)
         s->avoid_negative_ts = 1;
 
     if (!seg->write_header_trailer) {
-        close_null_ctx(oc->pb);
+        close_null_ctxp(&oc->pb);
         if ((ret = avio_open2(&oc->pb, oc->filename, AVIO_FLAG_WRITE,
                               &s->interrupt_callback, NULL)) < 0)
             goto fail;
@@ -820,7 +820,7 @@ static int seg_write_trailer(struct AVFormatContext *s)
             goto fail;
         open_null_ctx(&oc->pb);
         ret = av_write_trailer(oc);
-        close_null_ctx(oc->pb);
+        close_null_ctxp(&oc->pb);
     } else {
         ret = segment_end(s, 1, 1);
     }
@@ -836,7 +836,7 @@ fail:
     cur = seg->segment_list_entries;
     while (cur) {
         next = cur->next;
-        av_free(cur->filename);
+        av_freep(&cur->filename);
         av_free(cur);
         cur = next;
     }