avformat/options: don't call avformat_free_context() within avformat_alloc_context()

avformat_free_context() expects AVFormatContext->internal to not be NULL.
Reviewed-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
Signed-off-by: James Almer <jamrial@gmail.com>

libavformat/options.c

@@ -144,15 +144,17 @@ static void avformat_get_context_defaults(AVFormatContext *s)
 AVFormatContext *avformat_alloc_context(void)
 {
     AVFormatContext *ic;
+    AVFormatInternal *internal;
     ic = av_malloc(sizeof(AVFormatContext));
     if (!ic) return ic;
-    avformat_get_context_defaults(ic);
 
-    ic->internal = av_mallocz(sizeof(*ic->internal));
-    if (!ic->internal) {
-        avformat_free_context(ic);
+    internal = av_mallocz(sizeof(*internal));
+    if (!internal) {
+        av_free(ic);
         return NULL;
     }
+    avformat_get_context_defaults(ic);
+    ic->internal = internal;
     ic->internal->offset = AV_NOPTS_VALUE;
     ic->internal->raw_packet_buffer_remaining_size = RAW_PACKET_BUFFER_SIZE;
     ic->internal->shortest_end = AV_NOPTS_VALUE;