Fix undefined output (#118)

partly resolves coqui-ai/TTS#2798

Author: ppisljar

trainer/trainer.py

@@ -1619,6 +1619,7 @@ def eval_epoch(self) -> None:
         self.c_logger.print_eval_start()
         loader_start_time = time.time()
         batch = None
+        outputs = None
         for cur_step, batch in enumerate(self.eval_loader):
             # format data
             batch = self.format_batch(batch)