Replace NULL macros with nullptr literals.

Change-Id: I918c40879aa547438f77e7d1a95fa2aa33bec398
diff --git a/tests/cppbasic-shared/compute.cpp b/tests/cppbasic-shared/compute.cpp
index d93b453..6741d7a 100644
--- a/tests/cppbasic-shared/compute.cpp
+++ b/tests/cppbasic-shared/compute.cpp
@@ -42,7 +42,7 @@
         sc->set_elem(e);
         sc->set_type(t);
         sc->set_script(sc);
-        sc->set_script(NULL);
+        sc->set_script(nullptr);
         sp<const Sampler> samp = Sampler::CLAMP_NEAREST(rs);
         sc->set_sampler(samp);