Description of problem:
When publishing an errata (with 0 packages because of https://bugzilla.redhat.com/show_bug.cgi?id=655515) one gets a ISE

Version-Release number of selected component (if applicable):
Spacewalk 1.2

How reproducible:
Always

Steps to Reproduce:
1. Select channel on https://spacewalk.example.com/rhn/errata/manage/SelectChannels.do?eid=XY
2. Click on "Publish Errata"
3. ISE
4. Erratum is actually published
  
Actual results:
ISE

Expected results:
Avoid ISE

Additional info:

Is is useless to publish an erratum w/o packages, but is is working with Orcale XE, so this is considered to be connected to POstgreSQL.

PostgreSQL log shows the following:

ov 21 13:35:00 spacewalk-pg postgres[6014]: [8-1] ERROR:  cross-database references are not implemented: pe2.evr.as_vre_simple
Nov 21 13:35:00 spacewalk-pg postgres[6014]: [8-2] STATEMENT:  SELECT P1.id,
Nov 21 13:35:00 spacewalk-pg postgres[6014]: [8-3]             PN.name,
Nov 21 13:35:00 spacewalk-pg postgres[6014]: [8-4]             PE2.evr.as_vre_simple() || '.' || PA2.label AS current_nvrea,
Nov 21 13:35:00 spacewalk-pg postgres[6014]: [8-5]             PE1.evr.as_vre_simple() || '.' || PA1.label AS new_nvrea
Nov 21 13:35:00 spacewalk-pg postgres[6014]: [8-6]      FROM rhnPackage P1,
Nov 21 13:35:00 spacewalk-pg postgres[6014]: [8-7]           rhnPackageEVR PE1,
Nov 21 13:35:00 spacewalk-pg postgres[6014]: [8-8]           rhnPackageArch PA1,
Nov 21 13:35:00 spacewalk-pg postgres[6014]: [8-9]           rhnChannelNewestPackage CNP,
Nov 21 13:35:00 spacewalk-pg postgres[6014]: [8-10]          rhnPackageEVR PE2,
Nov 21 13:35:00 spacewalk-pg postgres[6014]: [8-11]          rhnPackageArch PA2,
Nov 21 13:35:00 spacewalk-pg postgres[6014]: [8-12]          rhnPackageName PN,
Nov 21 13:35:00 spacewalk-pg postgres[6014]: [8-13]          rhnErrataPackage EP
Nov 21 13:35:00 spacewalk-pg postgres[6014]: [8-14]     WHERE EP.errata_id = $1
Nov 21 13:35:01 spacewalk-pg postgres[6014]: [8-15]       AND P1.id = EP.package_id
Nov 21 13:35:01 spacewalk-pg postgres[6014]: [8-16]       AND CNP.channel_id = $2
Nov 21 13:35:01 spacewalk-pg postgres[6014]: [8-17]       AND P1.name_id = CNP.name_id
Nov 21 13:35:01 spacewalk-pg postgres[6014]: [8-18]       AND p1.package_arch_id = CNP.package_arch_id
Nov 21 13:35:01 spacewalk-pg postgres[6014]: [8-19]       AND PE1.id = P1.evr_id
Nov 21 13:35:01 spacewalk-pg postgres[6014]: [8-20]       AND PA1.id = P1.package_arch_id
Nov 21 13:35:01 spacewalk-pg postgres[6014]: [8-21]       AND PE2.id = CNP.evr_id
Nov 21 13:35:01 spacewalk-pg postgres[6014]: [8-22]       AND PA2.id = CNP.package_arch_id
Nov 21 13:35:01 spacewalk-pg postgres[6014]: [8-23]       AND PN.id = P1.name_id
Nov 21 13:35:01 spacewalk-pg postgres[6014]: [8-24]       AND rpm.vercmp(PE1.epoch, PE1.version, PE1.release, PE2.epoch, PE2.version, PE2.release) > 0