Why do I get 'Internal Server Error' when comparing packages between software channels or trying to merge software channels on Red Hat Satellite 5.7?

Issue

• When comparing packages between software channels or when trying to merge software channels on Red Hat Satellite 5.7, I get an Internal Server Error and the following tracebacks can be observed in the tomcat log files:

  2015-08-10 10:16:09,379 [TP-Processor664] ERROR com.redhat.rhn.common.db.datasource.CachedStatement - Error while processing cached statement sql: select  pn.name as package_name,
          pa.name as arch,
          ch1.package_id as left_id,
          evr_t_as_vre_simple(ch1.evr) as left_nvrea,
          ch2.package_id as right_id,
          evr_t_as_vre_simple(ch2.evr) as right_nvrea,
          case when ch1.evr_id is null then -2
               when ch2.evr_id is null then 2
               else rpm.vercmp(ch1.epoch, ch1.version, ch1.release,
                               ch2.epoch, ch2.version, ch2.release)
          end as comparison
    from (select np1.name_id, np1.package_arch_id, np1.evr_id, np1.package_id,
                  pe1.evr, pe1.epoch, pe1.version, pe1.release
            from rhnChannelNewestPackage np1
            join rhnPackageEvr pe1
              on pe1.id = np1.evr_id
          where channel_id = ?
          ) ch1
    full outer join (select np2.name_id, np2.package_arch_id, np2.evr_id, np2.package_id,
                          pe2.evr, pe2.epoch, pe2.version, pe2.release
                       from rhnChannelNewestPackage np2
                       join rhnPackageEvr pe2
                         on pe2.id = np2.evr_id
                      where channel_id = ?
          ) ch2
      on ch1.name_id = ch2.name_id
     and ch1.package_arch_id = ch2.package_arch_id
    join rhnPackageName pn
      on pn.id = coalesce(ch1.name_id, ch2.name_id)
    join rhnPackageArch pa
      on pa.id = coalesce(ch1.package_arch_id, ch2.package_arch_id)
   where ch1.evr_id is null
      or ch2.evr_id is null
      or ch1.evr_id != ch2.evr_id
  com.redhat.rhn.common.db.WrappedSQLException: ORA-30625: method dispatch on NULL SELF argument is disallowed
  ORA-06512: at "LXSAT_RSCE.EVR_T_AS_VRE_SIMPLE", line 5

        at com.redhat.rhn.common.translation.SqlExceptionTranslator.oracleSQLException(SqlExceptionTranslator.java:82)
        at com.redhat.rhn.common.translation.SqlExceptionTranslator.sqlException(SqlExceptionTranslator.java:42)
        at com.redhat.rhn.common.db.datasource.CachedStatement.processResultSet(CachedStatement.java:649)
        at com.redhat.rhn.common.db.datasource.CachedStatement.execute(CachedStatement.java:474)
        at com.redhat.rhn.common.db.datasource.CachedStatement.execute(CachedStatement.java:443)
        at com.redhat.rhn.common.db.datasource.CachedStatement.execute(CachedStatement.java:345)
        at com.redhat.rhn.common.db.datasource.CachedStatement.execute(CachedStatement.java:351)
        at com.redhat.rhn.common.db.datasource.CachedStatement.execute(CachedStatement.java:287)
        at com.redhat.rhn.common.db.datasource.SelectMode.execute(SelectMode.java:110)
        at com.redhat.rhn.manager.rhnpackage.PackageManager.comparePackagesBetweenChannels(PackageManager.java:994)
        at com.redhat.rhn.frontend.action.channel.manage.ChannelPackagesCompareAction.execute(ChannelPackagesCompareAction.java:115)
                                                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  [...]
  Caused by: 
  java.sql.SQLException: ORA-30625: method dispatch on NULL SELF argument is disallowed
  ORA-06512: at "LXSAT_RSCE.EVR_T_AS_VRE_SIMPLE", line 5