I am getting the nullpointer while displaying the controller code in vf using output panel .How can i resolve this

public class FAQCu {
public String selectedValue {get;set;}
public List<SelectOption> getUserType()
{
  List<SelectOption> options = new List<SelectOption>();   
   Schema.DescribeFieldResult fieldResult =FAQ__c.Users__c.getDescribe();
   List<Schema.PicklistEntry> ple = fieldResult.getPicklistValues();
    // options.add(new SelectOption('All','All'));
   for( Schema.PicklistEntry f : ple)
   {
      options.add(new SelectOption(f.getLabel(), f.getValue()));
   }   
   return options;
}
public List<FAQ__c> getSearch(){
        System.debug('====selectedValue===='+selectedValue); // You will get the Selected Value here
       
        List<FAQ__c> temp = new List<FAQ__c>();
     String queryString;
   if(selectedValue=='AllUsers')
   queryString='SELECT Users__c,Question__c,Answer__cfrom FAQ__c WHERE Users__c = \' AllUsers\' ';
   else if(selectedValue=='InternalUsers')
   queryString='SELECT Users__c,Question__c,Answer__cfrom FAQ__c WHERE Users__c = \' InternalUsers\' ';
   else if(selectedValue=='ExternalUsers')
queryString='SELECT Users__c,Question__c,Answer__cfrom FAQ__c WHERE Users__c = \' InternalUsers\' ';
temp = Database.query(queryString);
  
      return temp;
      }
    }
Vf page

<apex:page controller="FAQCu">
<apex:form >

<apex:selectList id="users" value="{!selectedValue}" size="1" required="true">
  <apex:selectOptions value="{!userType}"/>
</apex:selectList>
</apex:form>
</apex:page>

In the above vf where and what tags should i write to display theoutput?Please help on this

Thanks