nwc plugin: settings_dialog is wallet agnostic.

instead, test wallet in start_plugin.
prevent plugin from using several wallets.

electrum/plugins/nwc/nwcserver.py

@@ -42,6 +42,11 @@ class NWCServerPlugin(BasePlugin):
         self.logger.debug(f"NWCServerPlugin created, waiting for wallet to load...")
 
     def start_plugin(self, wallet: 'Abstract_Wallet'):
+        if not wallet.has_lightning():
+            return
+        if self.is_initialized:
+            # this might be called for several wallets. only use one.
+            return
         storage = self.get_plugin_storage(wallet)
         self.connections = storage['connections']
         self.delete_expired_connections()

electrum/plugins/nwc/qt.py

@@ -43,12 +43,6 @@ class Plugin(NWCServerPlugin):
                            partial(self.settings_dialog, window))
 
     def settings_dialog(self, window: WindowModalDialog):
-        wallet: 'Abstract_Wallet' = window.parent().wallet
-        if not wallet.has_lightning():
-            window.show_error(_("{} plugin requires a lightning enabled wallet. Setup lightning first.")
-                           .format("NWC"))
-            return
-
         d = WindowModalDialog(window, _("Nostr Wallet Connect"))
         main_layout = QVBoxLayout(d)