Fix null deref in sensors 2.0 VTS teardown am: b6b28e58c4 am: 0e70902d34
am: 2dc221df40

Change-Id: I09afaf33c649879ad71f0f4ed8de42a7a2a0b86a
diff --git a/sensors/2.0/vts/functional/SensorsHidlEnvironmentV2_0.cpp b/sensors/2.0/vts/functional/SensorsHidlEnvironmentV2_0.cpp
index be7415b..5f71654 100644
--- a/sensors/2.0/vts/functional/SensorsHidlEnvironmentV2_0.cpp
+++ b/sensors/2.0/vts/functional/SensorsHidlEnvironmentV2_0.cpp
@@ -109,11 +109,15 @@
 void SensorsHidlEnvironmentV2_0::HidlTearDown() {
     mStopThread = true;
 
-    // Wake up the event queue so the poll thread can exit
-    mEventQueueFlag->wake(asBaseType(EventQueueFlagBits::READ_AND_PROCESS));
-    mPollThread.join();
+    if (mEventQueueFlag != nullptr) {
+        // Wake up the event queue so the poll thread can exit
+        mEventQueueFlag->wake(asBaseType(EventQueueFlagBits::READ_AND_PROCESS));
+        if (mPollThread.joinable()) {
+            mPollThread.join();
+        }
 
-    EventFlag::deleteEventFlag(&mEventQueueFlag);
+        EventFlag::deleteEventFlag(&mEventQueueFlag);
+    }
 }
 
 void SensorsHidlEnvironmentV2_0::startPollingThread() {