fix compiler crash on forward declarations

diff --git a/Cython/Compiler/Symtab.py b/Cython/Compiler/Symtab.py
index c6a697af4bded76e0c51edba6a2a8fa0b4bab2a6..a560ead1ad07d44ce29a6ef4b4832a8d4e7d4a87 100644 (file)
--- a/Cython/Compiler/Symtab.py
+++ b/Cython/Compiler/Symtab.py
@@ -1020,7 +1020,7 @@ 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)