I am using the following trigger which should look at the case being created, make it a default admin user for the time being (for permissions), look only for WEB based bases to change the user ( which i think isn't working right either) and then add everyone with a checkbox on their contact as a case team member. However I get an error but ONLY when adding a case from our community. What about those users would mess this up?

trigger CaseTeamAddition on Case (after insert) {
 
  if (Trigger.isAfter){
                If (Trigger.isInsert){
                                CaseTeamRole caseTeamRole = [SELECT Id 
                                                            FROM CaseTeamRole 
                                                            WHERE Name = 'Case Update Team'
                                                            LIMIT 1];
 
                                List<Id> accountIdList = new List<Id>();
                          List<Id> caseIdList = new List<Id>();
                                For (Case currentCase : Trigger.new){
                                     accountIdList.add(currentCase.AccountId);
                                    caseIdList.add(currentCase.Id);
                                }
                          
                          User dbUser = [SELECT Id
                                                    FROM User
                                                    WHERE Alias = 'dblevins'
                                                    LIMIT 1];
                          
                          List<Case> caseList = [SELECT Id, OwnerId
                                                      FROM Case
                                                      WHERE Id IN :caseIdList
                                                      AND Type = 'Web'];
                          
                                for (Case curCase : caseList){
                                    curCase.OwnerId = dbUser.Id;
                                }
                          
                          update caseList;
                                
                                List<Contact> contactList = [SELECT Id, AccountId
                                                             FROM Contact
                                                             WHERE AccountId IN : accountIdList
                                                             AND Get_Email_Updates__c = true];
                                
                                List<CaseTeamMember> caseMembersToInsert = new List<CaseTeamMember>();
                                For (Case currentCase : Trigger.new){
                                  For (Contact currentContact : contactList){
                                     If (currentContact.AccountId == currentCase.AccountId){
                                           CaseTeamMember newMember = new CaseTeamMember(ParentId = currentCase.Id,
                                                                             MemberId = currentContact.Id,
                                                                                         TeamRoleId = caseTeamRole.Id);
                                            caseMembersToInsert.add(newMember);
                                        }
                                   }
                                }

                                if (caseMembersToInsert.size() > 0){
                                  insert caseMembersToInsert;
                                
                                }
                                                               
              }
  }