Reset drmPluginV1_1 when destroyPlugin is called.

Also check for NULL mDrmPlugin before casting to V1_1.

Test: Play Movies and NetFlix

bug: 72687425
Change-Id: I47aa18730332a17860b7e27440d417ffd612810f
diff --git a/drm/libmediadrm/DrmHal.cpp b/drm/libmediadrm/DrmHal.cpp
index d7816d7..07cec01 100644
--- a/drm/libmediadrm/DrmHal.cpp
+++ b/drm/libmediadrm/DrmHal.cpp
@@ -472,7 +472,9 @@
     for (size_t i = 0; i < mFactories.size(); i++) {
         if (mFactories[i]->isCryptoSchemeSupported(uuid)) {
             mPlugin = makeDrmPlugin(mFactories[i], uuid, appPackageName);
-            mPluginV1_1 = drm::V1_1::IDrmPlugin::castFrom(mPlugin);
+            if (mPlugin != NULL) {
+                mPluginV1_1 = drm::V1_1::IDrmPlugin::castFrom(mPlugin);
+            }
         }
     }
 
@@ -504,6 +506,7 @@
         }
     }
     mPlugin.clear();
+    mPluginV1_1.clear();
     return OK;
 }