cosmetic: indent

Originally committed as revision 16423 to svn://svn.ffmpeg.org/ffmpeg/trunk
diff --git a/libavutil/tree.c b/libavutil/tree.c
index bf485ab..008beb6 100644
--- a/libavutil/tree.c
+++ b/libavutil/tree.c
@@ -129,9 +129,9 @@
 
 void av_tree_destroy(AVTreeNode *t){
     if(t){
-    av_tree_destroy(t->child[0]);
-    av_tree_destroy(t->child[1]);
-    av_free(t);
+        av_tree_destroy(t->child[0]);
+        av_tree_destroy(t->child[1]);
+        av_free(t);
     }
 }