If you ever see the below People Search error go double check your indexed User Profile Properties.   I saw this recently and the root cause was a missing “Indexed” checkbox.   Enabling the Indexed checkbox for Account Name and crawling again fixed the issue.   Thanks to Puneet for the tip on this one.

System.NullReferenceException: Object reference not set to an instance of an object. at System.Xml.XmlNode.RemoveChild(XmlNode oldChild) at Microsoft.Office.Server.Search.WebControls.PeopleCoreResultsWebPart.DeleteElementAddToMyColleaguesURL(XmlNode result) at Microsoft.Office.Server.Search.WebControls.PeopleCoreResultsWebPart.CreateXmlDocument() at Microsoft.Office.Server.Search.WebControls.PeopleCoreResultsWebPart.SortBySocialDistance() at Microsoft.Office.Server.Search.WebControls.PeopleCoreResultsWebPart.GetXPathNavigator(String viewPath)

<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="xml" version="1.0" encoding="UTF-8" indent="yes"/>
<xsl:template match="/">
<xmp>
<xsl:copy-of select="*"/>
</xmp>
</xsl:template>
</xsl:stylesheet>