init ext sample rate to 0 if not present

Originally committed as revision 18139 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/mpeg4audio.c

@@ -61,9 +61,10 @@ int ff_mpeg4audio_get_config(MPEG4AudioConfig *c, const uint8_t *buf, int buf_si
         c->sbr = 1;
         c->ext_sample_rate = get_sample_rate(&gb, &c->ext_sampling_index);
         c->object_type = get_object_type(&gb);
-    } else
+    } else {
         c->ext_object_type = 0;
-
+        c->ext_sample_rate = 0;
+    }
     specific_config_bitindex = get_bits_count(&gb);
 
     if (c->ext_object_type != 5) {