Fix bug with construct_curr_info and test

ml-agents/mlagents/trainers/rl_trainer.py

         :return: curr_info: Reconstructed BrainInfo to match agents of next_info.
         """
         visual_observations: List[List[Any]] = [
-            []
+            [] for _ in next_info.visual_observations
         ]  # TODO add types to brain.py methods
         vector_observations = []
         text_observations = []

ml-agents/mlagents/trainers/tests/test_rl_trainer.py

 
     # assert construct_curr_info worked properly
     assert len(brain_info.agents) == 1
+    assert len(brain_info.visual_observations) == 1
+    assert len(brain_info.visual_observations[0]) == 1
+    assert len(brain_info.vector_observations) == 1
+    assert len(brain_info.previous_vector_actions) == 1
 
     # Test end episode
     trainer.end_episode()