C# check an element exists while using LINQ to XML

OK, bit of a random question, but the best way to do this is to just add the code, you'll be able to see what I mean straight away:

XML:

<?xml version="1.0" encoding="utf-8" ?>
<customers>
  <customer>
    <id>1</id>
    <name>Blah-face</name>
    <Type>1</Type>
  </customer>
  <customer>
    <id>2</id>
    <name>Blah-face-2</name>
    <Type>2</Type>
  </customer>
  <customer>
    <id>3</id>
    <name>Blah-face-3</name>
    <Type>1</Type>
    <SuperType>1</SuperType>
  </customer>
</customers>

C#:

XDocument linquee = XDocument.Load(path);

var superType = (from c in linquee.Descendants("customer")
                 where (c.Element("SuperType").Value == "1")
                 select c).ToList();

This comes up with a null error - would I need to add the "SuperType" element to each customer before it with a null value, or is there a workaround that would mean I don't have to do that?

Cheers!