output: #fixed code
                                  public SmsAlphabet getAlphabet()
      {
          switch (getGroup())
          {
          case GENERAL_DATA_CODING:
              // General Data Coding Indication
              if (dcs_ == 0x00)
              {
                  return SmsAlphabet.ASCII;
              }
  
              switch (dcs_ & 0x0C)
              {
              case 0x00: return SmsAlphabet.ASCII;
              case 0x04: return SmsAlphabet.LATIN1;
              case 0x08: return SmsAlphabet.UCS2;
              case 0x0C: return SmsAlphabet.RESERVED;
              default:   return SmsAlphabet.UCS2;
              }
              
          case MESSAGE_WAITING_STORE_GSM:
              return SmsAlphabet.ASCII;
          
          case MESSAGE_WAITING_STORE_UCS2:
              return SmsAlphabet.UCS2;
  
          case DATA_CODING_MESSAGE:
              switch (dcs_ & 0x04)
              {
              case 0x00: return SmsAlphabet.ASCII;
              case 0x04: return SmsAlphabet.LATIN1;
              default:   return SmsAlphabet.UCS2;
              }
          
          default:
              return SmsAlphabet.UCS2;
          }                
      }
input: #vulnerable code 
                                  public SmsAlphabet getAlphabet()
      {
          switch (getGroup())
          {
          case GENERAL_DATA_CODING:
              // General Data Coding Indication
              if (dcs_ == 0x00)
              {
                  return SmsAlphabet.ASCII;
              }
  
              switch (dcs_ & 0x0C)
              {
              case 0x00: return SmsAlphabet.ASCII;
              case 0x04: return SmsAlphabet.LATIN1;
              case 0x08: return SmsAlphabet.UCS2;
              case 0x0C: return SmsAlphabet.RESERVED;
              default:   return null;
              }
              
          case MESSAGE_WAITING_STORE_GSM:
              return SmsAlphabet.ASCII;
          
          case MESSAGE_WAITING_STORE_UCS2:
              return SmsAlphabet.UCS2;
  
          case DATA_CODING_MESSAGE:
              switch (dcs_ & 0x04)
              {
              case 0x00: return SmsAlphabet.ASCII;
              case 0x04: return SmsAlphabet.LATIN1;
              default:   return null;
              }
          
          default:
              return null;
          }                
      } 
                              #location 3 
                              #vulnerability type NULL_DEREFERENCE