Describe the bug
When you have moz-extension://.../notification.html open in a Firefox browser tab, and you Confirm a transaction, the entire browser window is closed, including all other (non-Metamask) tabs.

Steps to reproduce

1. Click the Metamask icon
2. Click the ... symbol
3. Click Expand View
4. In the URL bar, change home.html to notification.html and press Enter
5. Click Send
6. Enter any recipient
7. Enter any transaction amount/data
8. Click Next
9. Click Confirm.

Now the entire browser window closes, including other tabs that you had open in the same window as the Metamask notification.html tab.

Expected behavior
There are several possible expected behaviours:

1. No browser tabs or browser windows should close. The Metamask tab should return to /home.html or /notification.html
2. Only the Metamask notification.html tab should close
3. The option to Send from notification.html should not exist
   I prefer number 1.

Browser details

• OS: Windows 10
• Browser: Firefox 72.0 (64-bit)
• MetaMask Version: 7.7.1