Update QueryBuilder.cs

[markikordahi]

Check null before accessing nested object

[tghamm]

Hi @markikordahi thanks! I don't suppose you could write a quick unit test just to help me better understand the case this protects against for posterity could you?

[markikordahi]

i had the same issue "#61"
as an example, i have a student class and a Course class. student can have 0 1 or many classes.
when searching for allstudents with class name = "ABC" this was building below query which was throwing object not set to an instance of an object since Any was trying to access courses which is null (when student have 0 course)
item.Courses.AsQueryable().Any(Param_0 => ((True == True) AndAlso (Param_0.bookId.ToString().ToLower() == \"1\".ToLower())))
so now the query will look like this
((item.Courses != null) AndAlso item.Courses.AsQueryable().Any(Param_0 => ((True == True) AndAlso (Param_0.bookId.ToString().ToLower() == \"1\".ToLower()))))

[tghamm]

Thanks for clarifying, I'll take a look.