Stuck sending eth from non-selected account

[zxm04]

Describe the bug
When sending ETH, if you select "From" from an account other than the current selected one, clicking "next" would stuck with loading gif.

To Reproduce
Steps to reproduce the behavior:

1. Select "account 1"
2. Click on "Send"
3. Select "From" account with "account 2", set amount to 0.1
4. Click on "next"
5. Stuck with loading gif

Expected behavior
Send should be able to proceed.

Browser details (please complete the following information):

• OS: OSX
• Browser: Chrome
• MetaMask Version: 5.1.0

Additional context
Problem lies in https://github.com/MetaMask/metamask-extension/blob/develop/app/scripts/controllers/transactions/index.js#L178
In addUnapprovedTransaction, we have the check normalizedTxParams.from !== this.getSelectedAddress()