stagefright: handle NULL format after convertMetaDataToMessage

Bug: 30421366
Change-Id: I411f9f22b39943f7c8fa4e22fc37efe5f9e0ccb5
diff --git a/media/libmediaplayerservice/nuplayer/StreamingSource.cpp b/media/libmediaplayerservice/nuplayer/StreamingSource.cpp
index c4147e1..a7c5cf4 100644
--- a/media/libmediaplayerservice/nuplayer/StreamingSource.cpp
+++ b/media/libmediaplayerservice/nuplayer/StreamingSource.cpp
@@ -229,7 +229,8 @@
 
     sp<MetaData> meta = source->getFormat();
     status_t err = convertMetaDataToMessage(meta, &format);
-    if (err != OK) {
+    if (err != OK) { // format may have been cleared on error
+        format = new AMessage;
         format->setInt32("err", err);
     }
     return format;