Send screen- reset the amount to 0 if the user clicks the "add maximum" button on one coin and then selects another coin

[sinaizd]

Bug description if the user clicks the "add maximum" button on one coin and then selects another coin then the amount doesn't reset. This also applies to entering the amount manually,if the user entered the amount,and then changed the asset, the amount is reset to 0.

To Reproduce Steps to reproduce the behavior:

Go to the Send screen. The BEAM coin is selected by default Tap add max button. Select another coin. Current behavior: the amount doesn't reset.

Expected behavior:

the amount resets to 0.

Note: the wallet has some assets.

https://user-images.githubusercontent.com/45556620/126651039-7aed33d4-b946-4fa5-8dc8-d23301247fe0.mp4

[sinaizd]

not fixed:

This also applies to entering the amount manually,if the user entered the amount,and then changed the asset, the amount is reset to 0.

[KatsiarynaV]

The same behavior should be on the receive screen: if the user entered an amount and then changed the asset, the amount should resets to 0

[sinaizd]

checked