VT: fixes possible nullptr case in ARTPConnection.

[Problem] null pointer dereference happened in onPollStream()
[Cause] there is a possible case during getSelfID() called
  if mSource(vector) doesn't have any node.
[Solution] getSelfID() should be called by valid pointer.

Bug: 175657734

Change-Id: Ibec81df1c0455cefbd0414b7475fc622e5f4ddce
Signed-off-by: Byeongjo Park <bjo.park@samsung.com>
diff --git a/media/libstagefright/rtsp/ARTPConnection.cpp b/media/libstagefright/rtsp/ARTPConnection.cpp
index a4da433..4c69485 100644
--- a/media/libstagefright/rtsp/ARTPConnection.cpp
+++ b/media/libstagefright/rtsp/ARTPConnection.cpp
@@ -463,14 +463,16 @@
 
             if (err == -ECONNRESET) {
                 // socket failure, this stream is dead, Jim.
-                sp<AMessage> notify = it->mNotifyMsg->dup();
-                notify->setInt32("rtcp-event", 1);
-                notify->setInt32("payload-type", 400);
-                notify->setInt32("feedback-type", 1);
-                notify->setInt32("sender", it->mSources.valueAt(0)->getSelfID());
-                notify->post();
+                for (size_t i = 0; i < it->mSources.size(); ++i) {
+                    sp<AMessage> notify = it->mNotifyMsg->dup();
+                    notify->setInt32("rtcp-event", 1);
+                    notify->setInt32("payload-type", 400);
+                    notify->setInt32("feedback-type", 1);
+                    notify->setInt32("sender", it->mSources.valueAt(i)->getSelfID());
+                    notify->post();
 
-                ALOGW("failed to receive RTP/RTCP datagram.");
+                    ALOGW("failed to receive RTP/RTCP datagram.");
+                }
                 it = mStreams.erase(it);
                 continue;
             }