Copying code to clipboard omits empty lines in some files

[silverwind]

On some files like https://try.gitea.io/silverwind/symlink-test/src/branch/master/.drone.yml copying to clipboard via text selection omits emty lines in the copied content. The HTML of those empty lines does not render anything and I think we'd need to render a newline character for such empty lines so browser selection can properly pick it up. The issue does not show in all files and I think it's somehow caused by the yaml syntax highlighting.

On gitea (no newline character):

<code class="code-inner"><span class="w"></span></code>

On github (with newline character):

<td id="LC4" class="blob-code blob-code-inner js-file-line">
</td>

[silverwind]

Also of note, in diff view it works fine and the newline is there. Also there is no empty w span introduced by syntax highlighting which may be the culprit.

<code class="code-inner">
</code>