SPV: Protect getStorageClass() with a test that the thing is pointer.

Test/spv.bool.vert

@@ -0,0 +1,17 @@
+#version 450
+
+const bool condition = false;
+
+uniform ubname {
+    bool b;
+} ubinst;
+
+bool foo(bool b)
+{
+	return b != condition;
+}
+
+void main()
+{
+    gl_Position = foo(ubinst.b) ? vec4(0.0) : vec4(1.0);
+}