Revert "More fixes."

This reverts commit 37db7437cc08183a4218b502cf74aae887449b3b.
Assignments 1-4

Work on assignments 1 - 4
Revert "Revert "More fixes.""

This reverts commit b6c8e1a3a72713f0c405e155733d81665441c8f4.
Reverting mistake
Restored null initialization in assignment 4

Restored null initialization in assignment 4 to avoid reviewers'
comments for unnecessary change.
Changes?

Not sure why. Will just commit again.
What's wrong