Get The Value Of An XML Element Using Linq Even When Empty?

I am using ASP.NET in VB.

I have an XML document which contains all the details of staff in my company...

<staff>
<staffName>Test Staff</staffName>
<staffTitle>Slave</staffTitle>
<staffDepartmentName>Finance</staffDepartmentName>
<staffOffice>London</staffOffice>
<staffEmail>t.staff@company.co.uk</staffEmail>
<staffPhone>0207 123 456</staffPhone>
<staffNotes>Working hours Mon to Thurs 9.15 - 5.15</staffNotes>
<staffBio></staffBio>
</staff>

As you can see, some nodes do not always contain data for ever member of staff; only Directors have biographies.

I access the values like this...

For Each staff In ( _
From matches In myXMLFile.Descendants("staff").Descendants("staffName") _
Where matches.Nodes(0).ToString.ToLower.Contains(LCase(search)) _
Order By matches.Value _
Select matches)......

Once it gets to staffBio I get an error saying "Object reference not set to an instance of an object." obviously because that node does not exist.

My question is how can I assign the value to a variable even when it is empty without having to do a conditional check before each assignment?