Copy the below text from userreviewheader.html:
<div id="userbox_outer">
<div id="userbox">
<patTemplate:tmpl name="uh1" type="simplecondition" requiredvars="avg_user_rating" varscope="user_reviews_header">
<div id="userbox_h1"><patTemplate:translate>_JR_USER_RATING</patTemplate:translate></div>
<div id="userbox_h2">{AVG_USER_RATING}</div>
<div id="userbox_h3"><patTemplate:translate>_JR_OUT_OF_SCALE</patTemplate:translate> {RATING_SCALE}</div>
</patTemplate:tmpl>
<patTemplate:tmpl name="not_rated" visibility="hidden">
<div id="userbox_h4"><patTemplate:translate>_JR_NOT_RATED</patTemplate:translate></div>
</patTemplate:tmpl>
</div>
</div>
We edit it to replace the average rating tag with the correct one and add some patTemplate logic to check the review count and show the "not rated" text if there are no user reviews.
<div id="userbox_outer">
<div id="userbox">
<patTemplate:tmpl name="user_rating_box" type="condition" conditionvar="author_reviews_count" varscope="author_review_header">
<patTemplate:sub condition="0">
<div id="userbox_h4"><patTemplate:translate>_JR_NOT_RATED</patTemplate:translate></div>
</patTemplate:sub>
<patTemplate:sub condition="__default">
<div id="userbox_h1"><patTemplate:translate>_JR_USER_RATING</patTemplate:translate></div>
<div id="userbox_h2">{AUTHOR_USER_RATING}</div>
<div id="userbox_h3"><patTemplate:translate>_JR_OUT_OF_SCALE</patTemplate:translate> {RATING_SCALE}</div>
</patTemplate:sub>
</patTemplate:tmpl>
</div>
</div>
Paste the code in authorreviewheader.html