Fix a Bug, trainer_seq2seq.py, in the else branch at Line 172,...

Fix a Bug, trainer_seq2seq.py, in the else branch at Line 172, generation_inputs should be a dict (#14546)

* fix bug, trainer_seq2seq.py, Line 172, generation_inputs must be a dict before feeding into self.model.generation()

* fix bug, trainer_seq2seq.py, Line 172, generation_inputs must be a dict before feeding into self.model.generation()

src/transformers/trainer_seq2seq.py

@@ -169,7 +169,7 @@ class Seq2SeqTrainer(Trainer):
             # very ugly hack to make it work
             generation_inputs["input_ids"] = generation_inputs.pop(self.tokenizer.model_input_names[0])
         else:
-            generation_inputs = inputs["input_ids"]
+            generation_inputs = {"input_ids": inputs["input_ids"]}
 
         generated_tokens = self.model.generate(
             **generation_inputs,