[Glitch] Fix click event handling when clicking outside of an open dropdown menu

Port afdfeb5856 to glitch-soc

Signed-off-by: Claire <claire.github-309c@sitedethib.com>

app/javascript/flavours/glitch/components/dropdown_menu.jsx

@@ -39,6 +39,7 @@ class DropdownMenu extends PureComponent {
     if (this.node && !this.node.contains(e.target)) {
       this.props.onClose();
       e.stopPropagation();
+      e.preventDefault();
     }
   };