A Discoverer item:  while trying to edit some workbook items or when choosing Edit -> Condition , errors popped up like this:
“OracleBI Discoverer   :    java.lang.ArrayIndexOutOfBoundsException ”

“An error occurred while attempting to perform the operation.
The operation did not complete successfully.

Extra Internal Info:
(OLException
Cause:OLException {
Code: OLCmRefException::eNullRef
Args: OLCmRefException::eNullRef}}

Version Discoverer: 10.1.2.54.25

Doc ID:     559541.1:
After applying Discoverer Cumulative Patch 5 (Patch 6472361), or Cumulative Patch 6 (Patch 6669003) certain workbooks are failing to open or are reporting an error when editing conditions in Discoverer Plus.
Bug : 6933011

Solution in the doc is not quite self-confident:

1. Open a Support Request (SR) with Oracle Support and request the password for Discoverer Cumulative Patch 8, Patch 7306816.

2. Test the patch on a development or test server first.

3. Once the fix is confirmed, you may promote the patch to your production server environment.

Known Workaround

“If this problem is only occurring on a limited number of workbooks, you may recreate the workbook in Discoverer Plus.  Recreating and then re-saving the workbook eliminated the error in all cases.”

And that’s what we did….