.length error

@NONE@

The code below is in a button on the Customer Form.
It counts how many contacts a customer has within the search filters.

If the Customer doesn't have any Contacts I get this error:
TypeError 'length' is null or not an object.
How can I trap the error or find a way around this?

function xGetHowManyChildren()  {    var arrSearchFilter = new Array();          arrSearchFilter[0] = new nlobjSearchFilter('company',null,'is',nlapiGetRecordId());   arrSearchFilter[1] = new nlobjSearchFilter('custentitychildcentre', null, 'noneof', '@NONE@');     var arrSearchColumn = new Array();   arrSearchColumn[0] = new nlobjSearchColumn('firstname');   arrSearchColumn[1] = new nlobjSearchColumn('company');      var arrSearchResults = new Array();   arrSearchResults = nlapiSearchRecord('contact',null,arrSearchFilter,arrSearchColumn);       <span style="color:'"Blue"'"><strong>for (var i = 0; i &amp;lt; arrSearchResults.length; i++)</strong> </span>   {     var results = arrSearchResults[i];          if (results == undefined || results == null)    {     break;    }    else    {     var Col0 = results.getValue(arrSearchColumn[0]);     }    var ChildCount = Math.abs(i + 1);   }    alert("ChildCount: " + ChildCount;  }