FIX: References button for string ids

src/core/xsl/entity.xsl

@@ -52,7 +52,7 @@
   <xsl:template match="@id" mode="backreference-link">
     <a class="caosdb-backref-link btn caosdb-id-button" title="Find all entities which reference this one.">
       <xsl:attribute name="href">
-        <xsl:value-of select="concat($entitypath, '?P=0L10&amp;query=FIND+Entity+which+references+', current())"/>
+        <xsl:value-of select="concat($entitypath, '?P=0L10&amp;query=FIND+Entity+which+references+%22', current(), '%22')"/>
       </xsl:attribute>
       <span class="bg-dark badge d-none d-sm-inline">
         <i class="bi-link"></i> References