106 fix navigation bugs when not logged in

[claireolmstead]

Purpose

The goal of this PR is to better handle navigation and login errors when not logged in.

Closes #106

Solution

• When login is canceled, stop loading and don't throw error.
• If user tries to click on a profile while not logged in, a login modal opens.

Change summary

• Implemented above solutions

Steps to Verify

1. Logout
2. Try to click on user through the avatar in a post
3. see login modal pop up
4. login through modal
5. should be able to navigate everywhere
6. logout
7. login through header button

Additional details / screenshot