docs: public void checkNullableKey(BaseField field, boolean bFirstFieldOnly)
      {
          for (int iKeySeq = 0; iKeySeq < this.getRecord().getKeyAreaCount(); iKeySeq++)
          {
              KeyArea keyArea = this.getRecord().getKeyArea(iKeySeq);
              for (int iKeyFieldSeq = 0; iKeyFieldSeq < keyArea.getKeyFields(); iKeyFieldSeq++)
              {
                  if (keyArea.getField(iKeyFieldSeq) == field)
                  {
                      if (field.isNullable() == true)
                      {   // Don't allow this key to be null
                          field.setNullable(false);
                          return;
                      }
                  }
                  if (bFirstFieldOnly)
                      break;
              }
          }
      }