Fix shouldDisablePortalLogic in AppRootPortal

After refactoring in c7e4c41
We inversed the logic and forgot to inverse the mode condition too.
If we want to disablePortal in fallback we should disable the portal
when the mode='full'

That issue affected Snackbar position when it is used together with
Epic and tabbar.

packages/vkui/src/components/AppRoot/AppRootPortal.tsx

@@ -26,7 +26,7 @@ export const AppRootPortal = ({ children, usePortal }: AppRootPortalProps) => {
 
   const portalContainer = resolvePortalContainer(usePortal, portalRoot.current);
   if (!portalContainer || shouldDisablePortal(usePortal, mode, Boolean(disablePortal))) {
-    return children;
+    return <React.Fragment>{children}</React.Fragment>;
   }
 
   return createPortal(
@@ -47,7 +47,7 @@ function shouldDisablePortal(
     return disablePortal || usePortal !== true;
   }
   // fallback
-  return disablePortal || mode !== 'full';
+  return disablePortal || mode === 'full';
 }
 
 function resolvePortalContainer<PortalRootFromContext extends HTMLElement | null | undefined>(