Revert "And again."

This reverts commit a2a6ed05c5.

src/git-repository-async.js

@@ -660,11 +660,6 @@ export default class GitRepositoryAsync {
         }
         return this._diffBlobToBuffer(blob, text, options)
       })
-      .catch(e => {
-        // NB: I don't love this, but we're matching the behavior of
-        // `GitRepository` here for API compatibility.
-        return {}
-      })
   }
 
   // Checking Out