fix compiler crash on forward declarations

diff --git a/Cython/Compiler/Symtab.py b/Cython/Compiler/Symtab.py
index 8c7752efa0bd4b3798c1da762113d1b29aa37d50..b18947fa71951e9e71ac1ea57a04209c35f1539f 100644 (file)
--- a/Cython/Compiler/Symtab.py
+++ b/Cython/Compiler/Symtab.py
@@ -1022,7 +1022,7 @@ class ModuleScope(Scope):
             if defining or implementing:
                 scope = CClassScope(name = name, outer_scope = self,
                     visibility = visibility)
-                if base_type:
+                if base_type and base_type.scope:
                     scope.declare_inherited_c_attributes(base_type.scope)
                 type.set_scope(scope)
                 self.type_entries.append(entry)