Fix shutdown if HDCP was never instantiated.

Change-Id: Icdf6785880180f417c5432dff54c7e0fb12ef84d
related-to-bug: 7247918
diff --git a/media/libstagefright/wifi-display/source/WifiDisplaySource.cpp b/media/libstagefright/wifi-display/source/WifiDisplaySource.cpp
index 8091cc4..d5ffc65 100644
--- a/media/libstagefright/wifi-display/source/WifiDisplaySource.cpp
+++ b/media/libstagefright/wifi-display/source/WifiDisplaySource.cpp
@@ -1140,9 +1140,11 @@
     ALOGV("finishStop2");
 
 #if REQUIRE_HDCP
-    mHDCP->setObserver(NULL);
-    mHDCPObserver.clear();
-    mHDCP.clear();
+    if (mHDCP != NULL) {
+        mHDCP->setObserver(NULL);
+        mHDCPObserver.clear();
+        mHDCP.clear();
+    }
 #endif
 
     if (mSessionID != 0) {