qt receive_tab: fix "show_address_on_hw" functionality

follow-up b07fe970bf

I don't like this being hidden in the toolbar menu.
The other items in the toolbar menu are ~settings or generic actions
independent of the current request. This one is dependent on the
current request, and even the active "tab"... does not make sense
to show this when the lightning tab is active.
It is more difficult to discover it in the first place than previously,
and it being less visible goes against encouraging hw device users of
using it, which is what we should be doing.

Anyway, this commit just makes it functional as-is.

electrum/gui/qt/receive_tab.py

@@ -252,6 +252,8 @@ class ReceiveTab(QWidget, MessageBoxMixin, Logger):
         req = self.wallet.get_request(key) if key else None
         if req is None:
             self.receive_e.setText('')
+            self.addr = self.URI = self.lnaddr = ''
+            self.address_help = self.URI_help = self.ln_help = ''
             return
         help_texts = self.wallet.get_help_texts_for_receive_request(req)
         self.addr = (req.get_address() or '') if not help_texts.address_is_error else ''
@@ -357,6 +359,8 @@ class ReceiveTab(QWidget, MessageBoxMixin, Logger):
 
     def do_clear(self):
         self.receive_e.setText('')
+        self.addr = self.URI = self.lnaddr = ''
+        self.address_help = self.URI_help = self.ln_help = ''
         self.receive_widget.setVisible(False)
         self.toggle_qr_button.setEnabled(False)
         self.toggle_view_button.setEnabled(False)

electrum/plugins/hw_wallet/qt.py

@@ -284,13 +284,13 @@ class QtPluginBase(object):
                                                               keystore: 'Hardware_KeyStore',
                                                               main_window: ElectrumWindow):
         plugin = keystore.plugin
-        receive_address_e = main_window.receive_tab.receive_address_e
+        receive_tab = main_window.receive_tab
 
         def show_address():
-            addr = str(receive_address_e.text())
+            addr = str(receive_tab.addr)
             keystore.thread.add(partial(plugin.show_address, wallet, addr, keystore))
         dev_name = f"{plugin.device} ({keystore.label})"
-        main_window.receive_tab.toolbar_menu.addAction(read_QIcon("eye1.png"), _("Show address on {}").format(dev_name), show_address)
+        receive_tab.toolbar_menu.addAction(read_QIcon("eye1.png"), _("Show address on {}").format(dev_name), show_address)
 
     def create_handler(self, window: Union[ElectrumWindow, InstallWizard]) -> 'QtHandlerBase':
         raise NotImplementedError()