get the null,blank value from the table

I want to get the value which is [null],blank or space from the field 'category_type' from the table I want to get fetch the [null],blank,'Uncategorized' or space in category_type. Now I can able to get only blank value .need to get null value too.how to get the null value field also in postgres db in laravel query.

I have the created the variable $category=[]

if(in_array('Uncategorized',$category)){
          $category[]='';    
        $category[]='-';                  
        $category[]=' ';                  
        $category[]=null;                 
     }
 $table=DB::('category')->where('category.category_type',$category)->pluck('name')->toArray();

via Chebli Mohamed