HTML report is not generated when message is empty

[muraczewski]

When the message in failed assertion is empty, then the exception is thrown and the HTML report is not generated

<assertions> <assertion result="Failed"> <message><![CDATA[]]></message> <stack-trace><![CDATA[here is a stack trace but I cannot share it]]></stack-trace> </assertion> </assertions>

[muraczewski]

I cannot commit my changes. Here is fix