Fix Coverity #158: Check the correct variable.
diff --git a/Python/ast.c b/Python/ast.c
index 956ee20..525b5a6 100644
--- a/Python/ast.c
+++ b/Python/ast.c
@@ -1468,7 +1468,7 @@
                 tmp_result = BinOp(result, newoperator, tmp, 
                                    LINENO(next_oper), next_oper->n_col_offset,
                                    c->c_arena);
-                if (!tmp) 
+                if (!tmp_result) 
                         return NULL;
                 result = tmp_result;
         }