Error While Using Querystrings

i made a page in asp using querystrings for get some data and when i put in one of the variables in blank in the address bar i get this error:

Microsoft VBScript runtime error '800a000d'

Type mismatch: '[string: ""]'

/history.asp, line 82

i don't know how to fix it...in my code i have sth like this:

If Request.QueryString("var1")="sth" AND Request.QueryString("var2")>0 Then
'make some process
End If

so in the "var2" when it's empty i get an error :/ should i do another if for when is it empty just for in some way "handle" it and don't let occure problems while some user does sth like that??