tasks #7266: Delete docman index when there is no data doesn't throw any error

This task is part of story #7185 Search in existing wiki pages

Change-Id: I5ded735992018f2c513792694e12e483b557f7bc
Merge commit 'refs/changes/00/2800/3' of ssh://gerrit.tuleap.net:29418/tuleap into tuleap-stable-master

* ssh://gerrit.tuleap.net:29418/tuleap:
  tasks #7266: Delete docman index when there is no data doesn't throw any error

Change-Id: Ia0315bda45ea2b20a369683790aff4285790366c
Tuleap 7.3.99.5

Change-Id: I3c64f3325a4643871b56ef260ad2aa380a3bc5da