SEND: disable paste button when there is nothing to paste / clipboard empty

[MarnixCroes]

1. manually type in an address
2. you want to go back and check something in your wallet
3. you click the paste icon, thinking it is a copy
4. your clipboard is empty
5. the address gets wiped and replaced with emptiness

Solution

Do not paste/wipe the entry if the clipboard is empty and clicking the paste button. There is no reason.