PLT-4486 Don't apply sidebar bg color to settings modals w/o tabs (#4460)

* PLT-4486 Don't apply sidebar bg color to settings modals w/o tabs

* PLT-4486 Use more correct naming for tabless modals

webapp/components/channel_notifications_modal.jsx

@@ -382,7 +382,7 @@ export default class ChannelNotificationsModal extends React.Component {
         return (
             <Modal
                 show={this.state.show}
-                dialogClassName='settings-modal'
+                dialogClassName='settings-modal settings-modal--tabless'
                 onHide={this.onHide}
                 onExited={this.props.onHide}
             >

webapp/utils/utils.jsx

@@ -465,7 +465,7 @@ export function applyTheme(theme) {
     if (theme.sidebarBg) {
         changeCss('.sidebar--left, .sidebar--left .sidebar__divider .sidebar__divider__text, .app__body .modal .settings-modal .settings-table .settings-links, .app__body .sidebar--menu', 'background:' + theme.sidebarBg, 1);
         changeCss('body.app__body', 'scrollbar-face-color:' + theme.sidebarBg, 3);
-        changeCss('@media(max-width: 768px){.app__body .modal .settings-modal:not(.display--content) .modal-content', 'background:' + theme.sidebarBg, 1);
+        changeCss('@media(max-width: 768px){.app__body .modal .settings-modal:not(.settings-modal--tabless):not(.display--content) .modal-content', 'background:' + theme.sidebarBg, 1);
     }
 
     if (theme.sidebarText) {