Fix NPD in GrallocWrapper

Avoid dereferencing null if mapper service is not available.

Bug: 135638664
Test: run VtsHalSensorsV2_0TargetTest
Change-Id: I3cf2a9f152d8f1737cb5a94356e252d54156c716
diff --git a/sensors/common/vts/utils/GrallocWrapper.cpp b/sensors/common/vts/utils/GrallocWrapper.cpp
index 153c208..222ef96 100644
--- a/sensors/common/vts/utils/GrallocWrapper.cpp
+++ b/sensors/common/vts/utils/GrallocWrapper.cpp
@@ -33,8 +33,7 @@
     mMapper = mapper2::IMapper::getService();
     if (mMapper == nullptr) {
         ALOGE("Failed to get mapper service");
-    }
-    if (mMapper->isRemote()) {
+    } else if (mMapper->isRemote()) {
         ALOGE("Mapper is not in passthrough mode");
     }
 }