<apex:page standardcontroller="METADATA_Campaign__c" extensions="CampaignPage" showHeader="false" sidebar="false">
  <style>
        body .bPageBlock .pbBody .red .pbSubheader{
            background-color:#c00000;
        }
        body .bPageBlock .pbBody .grey .pbSubheader{
            background-color:#c0c0c0;
        }
        body .bPageBlock .pbBody .grey .pbSubheader h3{
            color:#000;
        }
        body .bPageBlock .pbBody .blue .pbSubheader{
            background-color:#0000FF;
        }        
    </style>
       <apex:form >
    <apex:pageBlock title="Campaign Details">
  
                <apex:outputPanel styleClass="Red" >
                <apex:pageblockSection title="Campaign Information">
                        <apex:inputField value="{!camp.Name}"/>
     <apex:inputField value="{!camp.BRANDED__c}"/>
     <apex:inputField value="{!camp.METADATA_Status__c}"/>
     <apex:inputField value="{!camp.Program__c}"/>
     <apex:inputField value="{!camp.Therapy_Class__c}"/>
     <apex:inputField value="{!camp.Campaign_Code__c}"/>
     <apex:inputField value="{!camp.Campaign_ID__c}"/>
     <apex:inputField value="{!camp.Campaign_Type__c}"/>
     <apex:inputField value="{!camp.EndDate__c}"/>
     <apex:inputField value="{!camp.HCP__c}"/>
     <apex:inputField value="{!camp.Objective__c}"/>
     <apex:inputField value="{!camp.Description__c}"/>
     
     <apex:inputField value="{!camp.Program_ID__c}"/>
     <apex:inputField value="{!camp.StartDate__c}"/>
    
     <apex:inputField value="{!camp.Status__c}"/>
     <apex:inputField value="{!camp.Therapy_ClassID__c}"/>
     
     <apex:inputField value="{!camp.UA_CAMPAIGN_ID__c}"/>
     <apex:inputField value="{!camp.USMM__c}"/> 
                </apex:pageblockSection>
            </apex:outputPanel>
     <apex:pageBlockButtons >
    <apex:commandButton value="Save" action="{!save}"/>
   </apex:pageBlockButtons>

  </apex:pageBlock> 
  </apex:form> 
</apex:page>

//

Above VF Page is my Custom page, when i click sava the  record not saving and showing error that 'Attempted to upsert a null list
Error is in expression '{!save}' in component <apex:commandButton> in page metadatacampaignpage: Class.CampaignPage.save: line 14, column 1


here i am attaching my Apex class please saove this... Its urgent..

Thanks in Advance

public class CampaignPage {

    public CampaignPage(ApexPages.StandardController controller) {
    }
  public Metadata_Campaign__c camp;

   public void insertcampaign(){
   camp = [select id,BRANDED__c,Campaign_Code__c,Campaign_ID__c,Campaign_Type__c,Description__c,EndDate__c,HCP__c,Objective__c,Program__c,Program_ID__c,StartDate__c,  METADATA_Status__c,Status__c,Therapy_ClassID__c,Therapy_Class__c,UA_CAMPAIGN_ID__c,USMM__c from METADATA_Campaign__c where id =: ApexPages.currentPage().getParameters().get('id')];
   }
    public Metadata_Campaign__c getcamp(){
    return camp;
 }
   public system.PageReference save() {
    Upsert camp;
  PageReference pref = new ApexPages.StandardController(camp).view();
   return pref;
  }
  }
'