When attempting to Build our Addressable Asset Bundles Unity started throwing 'ArgumentException: Path is empty.' and 'FileNotFoundException' from HashingMethods.CalculateFile() at line 294. Upon investigating the cause of these Exceptions User found that they were coming from the Build Cache referencing Assets in their Dependencies that had been removed from the project.

To reproduce:

1. Download attached project “Addressables Dependancy Bug.zip" and open in Unity
2. Open “SampleScene” scene
3. Press Custom > Build Bundles menu item and wait until it completes
4. Delete the script "ReferenceScript" and remove its reference on the "MainPrefab" prefab
5. Press Custom > Build Bundles menu item again

Expected results: Addressables succeeds to build again
Actual results: Addressables fails to build and throws "ArgumentException: Path is empty" or "FileNotFoundException" from HashingMethods.CalculateFile() at line 294

Notes:
- This issue appears on both Windows and macOS
- This behavior causes thousands of LODGroups to become outdated while working on an actual level.
- Workaround: Delete Build Cache from Library folder
- Could not check on earlier Unity versions because the project becomes corrupted

Reproduced on Unity 2018.2.17f1, 2018.2.20f1, 2018.3.1f1 and 2019.1.0a12