fix optimizer update parameter is uninitialized

python/paddle/optimizer/optimizer.py

@@ -1193,15 +1193,24 @@ def _create_optimization_pass(
                         self._set_auxiliary_var('found_inf', False)
                     if isinstance(parameters_and_grads, list):
                         for param_and_grad in parameters_and_grads:
-                            if param_and_grad[1] is None:
+                            # Parameters can be uninitialized in pipeline parallel of semi-auto parallel.
+                            # Since gradient clip and parameters update mixed up in one interface, so we
+                            # need to filter again here.
+                            if (
+                                param_and_grad[1] is None
+                                or not param_and_grad[0]._is_initialized()
+                            ):
                                 continue
                             if param_and_grad[0].stop_gradient is False:
                                 self._append_optimize_op(
                                     target_block, param_and_grad
                                 )
                     else:
                         for param_and_grad in parameters_and_grads['params']:
-                            if param_and_grad[1] is None:
+                            if (
+                                param_and_grad[1] is None
+                                or not param_and_grad[0]._is_initialized()
+                            ):
                                 continue
                             if param_and_grad[0].stop_gradient is False:
                                 param_grad_dict = {}