re PR c++/5453 (Compiled program crash - inheritance/template/friend class problem)

PR c++/5453
        * class.c (fixed_type_or_null): Fix thinko.

From-SVN: r49135

gcc/testsuite/g++.dg/inherit/null1.C

@@ -0,0 +1,15 @@
+// PR c++/5453: Test that we don't assume that the pointer target of a
+// reference is non-null just because we know the reference isn't.
+
+// { dg-do run }
+
+struct V { };
+struct A: virtual public V { };
+
+A* ap;
+A*& apr (ap);
+
+int main ()
+{
+  V* vp = apr;
+}