recent_topics: Return false in `is_in_focus` if a modal is present.

This prevents a bug where keypresses are received by recent_topics view
even if a modal is present on it, which prevents, for instance, the modal
from receiving text input.

static/js/recent_topics_util.js

@@ -16,6 +16,7 @@ export function is_in_focus() {
         !compose_state.composing() &&
         !popovers.any_active() &&
         !overlays.is_active() &&
+        !overlays.is_modal_open() &&
         !$(".home-page-input").is(":focus")
     );
 }