Fix crash for classes with ignored base class

This fixes class_ignore.cpptest.

Examples/test-suite/c/Makefile.in

@@ -101,7 +101,6 @@ SWIGOPT += -w524 # Suppress SWIGWARN_LANG_EXPERIMENTAL warning
 # Tests for which C++ wrappers currently don't compile.
 apply_strings.cpptest \
 autodoc.cpptest \
-class_ignore.cpptest \
 class_scope_weird.cpptest \
 contract.cpptest \
 conversion.cpptest \

Source/Modules/c.cxx

@@ -983,7 +983,8 @@ public:
 	first_base_ = Copy(i.item);
       }
 
-      Printv(base_classes, " : public ", Getattr(first_base_, "sym:name"), NIL);
+      if (first_base_)
+	Printv(base_classes, " : public ", Getattr(first_base_, "sym:name"), NIL);
     }
 
     Printv(cxx_wrappers_.sect_types,