Only allow to expand the "buildsystem" plugin output when there is something to expand

debexpo/templates/plugins/buildsystem/html.mako

 <div class="qa-header">
 Buildsystem: ${o.outcome}
 </div>
-<div class="qa-content">
 %if o.rich_data["build-system"] == "debhelper":
+<div class="qa-content">
 %if o.rich_data["compat-level"]:
 Debhelper compatibility level ${o.rich_data["compat-level"]}
 %else:
 No compatibility level set!
 %endif
+</div>
 %endif
-</div>
\ No newline at end of file