Message signing with bech32 addresses crashes Electrum

[SomberNight]

Signing messages with p2wpkh and p2wpkh-p2sh addresses is not standardized (yet?), see e.g. bitcoin/bitcoin#10542
I think for the time being it can be disabled altogether, which is also what the current code (91ed74a) aims to do:

electrum/gui/qt/main_window.py

Lines 1901 to 1903 in 91ed74a

	if not bitcoin.is_p2pkh(address):
	self.show_message('Cannot sign messages with this type of address.' + '\n\n' + self.msg_sign)
	return

Though perhaps this remark needs updated?

electrum/gui/qt/main_window.py

Lines 1890 to 1892 in 91ed74a

	"private key, and verifying with the corresponding public key. The "
	"address you have entered does not have a unique public key, so these "
	"operations cannot be performed.")

However, on current master, trying to sign a message with a bech32 address results in a crash:

Traceback (most recent call last):
  File "/home/user/wspace/electrum/gui/qt/main_window.py", line 1957, in <lambda>
    b.clicked.connect(lambda: self.do_sign(address_e, message_e, signature_e))
  File "/home/user/wspace/electrum/gui/qt/main_window.py", line 1281, in request_password
    return func(self, *args, **kwargs)
  File "/home/user/wspace/electrum/gui/qt/main_window.py", line 1901, in do_sign
    if not bitcoin.is_p2pkh(address):
  File "/home/user/wspace/electrum/lib/bitcoin.py", line 562, in is_p2pkh
    addrtype, h = b58_address_to_hash160(addr)
  File "/home/user/wspace/electrum/lib/bitcoin.py", line 314, in b58_address_to_hash160
    return _bytes[0], _bytes[1:21]
TypeError: 'NoneType' object is not subscriptable
Aborted

[lzsaver]

The same thing if I try to send coins to the bech32 address (#2976).

[ecdsa]

added in e299df7

[prusnak]

@ecdsa you should have used the scheme proposed in bitcoin/bitcoin#10542 (comment)