Remove some new memory leaks from SensorManager

After catching an error in Sensor::unflatten, there are memory leaks
caught by the fuzzer in the same test case.

Test: libsensorserviceaidl_fuzzer with testcase from bug
Bug: 269014004
Merged-In: I509cceb41f56ca117d9475f6f6674244560fe582
Change-Id: I509cceb41f56ca117d9475f6f6674244560fe582
diff --git a/libs/sensor/SensorManager.cpp b/libs/sensor/SensorManager.cpp
index 2748276..8e0ea6c 100644
--- a/libs/sensor/SensorManager.cpp
+++ b/libs/sensor/SensorManager.cpp
@@ -166,6 +166,11 @@
 
         mSensors = mSensorServer->getSensorList(mOpPackageName);
         size_t count = mSensors.size();
+        if (count == 0) {
+            ALOGE("Failed to get Sensor list");
+            mSensorServer.clear();
+            return UNKNOWN_ERROR;
+        }
         mSensorList =
                 static_cast<Sensor const**>(malloc(count * sizeof(Sensor*)));
         LOG_ALWAYS_FATAL_IF(mSensorList == nullptr, "mSensorList NULL");