Prevent basic auth with both empty username and password

On ios the native basic auth prompt does not work with both an empty username and password.
In case both are empty, the "login" button is disabled and can't be pressed.

src/modules/settings/screens/ServerSettings.tsx

@@ -285,18 +285,21 @@ export const ServerSettings = () => {
                     <Switch
                         edge="end"
                         checked={serverSettings.basicAuthEnabled}
+                        disabled={!serverSettings.basicAuthUsername.trim() && !serverSettings.basicAuthPassword.trim()}
                         onChange={(e) => updateSetting('basicAuthEnabled', e.target.checked)}
                     />
                 </ListItem>
                 <TextSetting
                     settingName={t('settings.server.auth.basic.label.username')}
                     value={serverSettings.basicAuthUsername}
+                    validate={(value) => !serverSettings.basicAuthEnabled || !!value.trim()}
                     handleChange={(authUsername) => updateSetting('basicAuthUsername', authUsername)}
                 />
                 <TextSetting
                     settingName={t('settings.server.auth.basic.label.password')}
                     value={serverSettings.basicAuthPassword}
                     isPassword
+                    validate={(value) => !serverSettings.basicAuthEnabled || !!value.trim()}
                     handleChange={(authPassword) => updateSetting('basicAuthPassword', authPassword)}
                 />
             </List>