GenericSource: reset mDrmManagerClient when mDataSource is cleared.

Bug: 25070434
Change-Id: Iade3472c496ac42456e42db35e402f7b66416f5b
diff --git a/media/libmediaplayerservice/nuplayer/GenericSource.cpp b/media/libmediaplayerservice/nuplayer/GenericSource.cpp
index b3eb5fd..42fcb5b 100644
--- a/media/libmediaplayerservice/nuplayer/GenericSource.cpp
+++ b/media/libmediaplayerservice/nuplayer/GenericSource.cpp
@@ -474,6 +474,7 @@
             {
                 Mutex::Autolock _l(mDisconnectLock);
                 mDataSource.clear();
+                mDrmManagerClient = NULL;
                 mCachedSource.clear();
                 mHttpSource.clear();
             }