Updated mediawiki/extensions
Project: mediawiki/extensions/Flow  51f0fdac4dd8f0989cebce54e5d8dfe446ff7a65

Avoid abstract function errors in php 5.3.3

Same fix as change I183f96e960 , in a different class.
Bug: 53523

Change-Id: I97ee720c2e987a1686c5c2801b434e1cfd72c13a