Warn users who enter a "To" address of 0x0000000000000000000000000000000000000000 in the "Send Ether" page

[ltfschoen]

0x0000000000000000000000000000000000000000 is a valid Ethereum address and the "Address" input field currently considers it valid.
This is correct since it's a proof-of-burn account and normally sending to 0x0000000000000000000000000000000000000000 is used as a mechanism to verifiably burn/destroy Ether or tokens on the assumption that noone has the private key for that address.

But I think we should at least protect users from making mistakes by showing a "warning" tooltip if they enter the value of 0x0000000000000000000000000000000000000000 for the "Amount" incase burning/destroying their Ether wasn't their intention.

Some wallet UIs have been known to not provide sufficient safeguards to protect users by means of input field validation or tooltip warnings. For example sending transactions to 0x0000000000000000000000000000000000000000 by default if a user forgot to enter a value for the recipient address before clicking send.

[Tbaut]

I'd be for marking the 0x0 address as invalid as a quick and good enough solution.

[DrZainAzm]

• Send 8400 ether to 0xc287cf1f50d5bd56de70bdec1f4103d2b733a6d4 from account 0xed5a231ecc0fa775980ad7b86e49872feacd4c8f.
• Wallet ÐApp handling account 0x0000000000000000000000000000000000000000 requests authorisation to conduct the above through: Message from 0xf1833AeFFb5C625BC81d36037F8f790e562c0c1c to 0x0000000000000000000000000000000000000000 to: Send 8400 ether to 0xc287cf1f50d5bd56de70bdec1f4103d2b733a6d4
• a7bd8721477c6a497cf1b6e09f027808ed6e7bb0bd6766ebfc15e7067ed7093e

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