don't crash when a generator has more than 3 arguments and kwargs

src/runtime/generator.cpp

@@ -467,7 +467,7 @@ extern "C" BoxedGenerator::BoxedGenerator(BoxedFunctionBase* function, Box* arg1
         this->args = new (numArgs) GCdArray();
         memcpy(&this->args->elts[0], args, numArgs * sizeof(Box*));
         for (int i = 0; i < numArgs; i++) {
-            Py_INCREF(args[i]);
+            Py_XINCREF(args[i]);
         }
     }
 

test/tests/generators.py

@@ -142,3 +142,8 @@ def this_is_not_generator():
     def f():
         yield
 print type(this_is_not_generator())
+
+# we used to crash when a generator had more than 3 arguments and kwargs (because they can be NULL)
+def G(a, b, c, *args, **kwargs):
+    yield 1
+print list(G(1,2,2))