Problems with automatic_optimization=False
🐛 Bug

When automatic_optimization = False and terminate_on_nan = True, an exception is raised when checking for nan values. This is due to None being passed in as the value for loss to self.detect_nan_tensors. It looks like the code on master has already changed from what I'm seeing in 1.0.3, so I don't know if this has somehow been fixed or not. The problem seems to be that the AttributeDict returned from train_step has loss=None.
Please reproduce using the BoringModel and post here

https://colab.research.google.com/drive/1qQmP6BwQk--rBXC7W45y0mn6QK39IPcc
Expected behavior
Don't crash when automatic_optimization = False and terminate_on_nan = True