[VP] Fix converity issue by legacy code changed

Fix converity issue by legacy code changed.
diff --git a/media_driver/agnostic/common/vp/hal/vphal_render_composite.cpp b/media_driver/agnostic/common/vp/hal/vphal_render_composite.cpp
index 20eb49e..1690302 100644
--- a/media_driver/agnostic/common/vp/hal/vphal_render_composite.cpp
+++ b/media_driver/agnostic/common/vp/hal/vphal_render_composite.cpp
@@ -1944,8 +1944,11 @@
     PVPHAL_COMPOSITE_PARAMS     pComposite,
     PVPHAL_SURFACE              pTarget)
 {
-    bool    bResult;
-
+    bool    bResult = false;
+    if (nullptr == pTarget)
+    {
+        return bResult;
+    }
     // Set render target
     pComposite->Target[0] = *pTarget;