Add additional drm hal tests

Test: VTS tests passing

bug:34178477
Change-Id: Ie8fa5f2ad193b717b0564bb3046de8a64ccd8d85
diff --git a/drm/1.0/default/DrmPlugin.cpp b/drm/1.0/default/DrmPlugin.cpp
index c7428a5..e9133ac 100644
--- a/drm/1.0/default/DrmPlugin.cpp
+++ b/drm/1.0/default/DrmPlugin.cpp
@@ -327,19 +327,25 @@
 
     Return<void> DrmPlugin::sendEvent(EventType eventType,
             const hidl_vec<uint8_t>& sessionId, const hidl_vec<uint8_t>& data) {
-        mListener->sendEvent(eventType, sessionId, data);
+        if (mListener != nullptr) {
+            mListener->sendEvent(eventType, sessionId, data);
+        }
         return Void();
     }
 
     Return<void> DrmPlugin::sendExpirationUpdate(
             const hidl_vec<uint8_t>& sessionId, int64_t expiryTimeInMS) {
-        mListener->sendExpirationUpdate(sessionId, expiryTimeInMS);
+        if (mListener != nullptr) {
+            mListener->sendExpirationUpdate(sessionId, expiryTimeInMS);
+        }
         return Void();
     }
 
     Return<void> DrmPlugin::sendKeysChange(const hidl_vec<uint8_t>& sessionId,
             const hidl_vec<KeyStatus>& keyStatusList, bool hasNewUsableKey) {
-        mListener->sendKeysChange(sessionId, keyStatusList, hasNewUsableKey);
+        if (mListener != nullptr) {
+            mListener->sendKeysChange(sessionId, keyStatusList, hasNewUsableKey);
+        }
         return Void();
     }