Route slots are multiplying after each route change #173
Description
Since 9.0.0 the content of one of my routes keeps adding the slot to the dom everytime route change is triggered.
This is the route element.
<route class="header" path="/:p+">
<header class="cat-header">
<button class="back" onclick="history.back()">Back</button>
<div>
<button class="search"></button>
</div>
<div class="cat-image"></div>
</header>
</route>
You can see that after every change of route the header is being added again.