Fix exception in markdown renderer — radicle-desktop

To reproduce: open the gobble repo in the patches listing and switch between the two open patches repeatedly. You should see an exception in the dev console pop up mentioning the Markdown.svelte renderer.

Fixes this issue.

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     content;
     void tick().then(() => {
       // Don't run this if the component hasn't mounted yet.
       if (container === null) {
         return;
       }
       for (const e of container.querySelectorAll("a")) {
         try {
           const url = new URL(e.href);