watch-only wallets can't sign or decrypt messages

gui/qt/main_window.py

@@ -2119,6 +2119,9 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, PrintError):
         if not bitcoin.is_address(address):
             self.show_message(_('Invalid Bitcoin address.'))
             return
+        if self.wallet.is_watching_only():
+            self.show_message(_('This is a watching-only wallet.'))
+            return
         if not self.wallet.is_mine(address):
             self.show_message(_('Address not in wallet.'))
             return
@@ -2189,6 +2192,9 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, PrintError):
 
     @protected
     def do_decrypt(self, message_e, pubkey_e, encrypted_e, password):
+        if self.wallet.is_watching_only():
+            self.show_message(_('This is a watching-only wallet.'))
+            return
         cyphertext = encrypted_e.toPlainText()
         task = partial(self.wallet.decrypt_message, pubkey_e.text(), cyphertext, password)
         self.wallet.thread.add(task, on_success=lambda text: message_e.setText(text.decode('utf-8')))