The Warner Bros. studio in Leavesden was the location for the filming of the Harry Potter movies, and is now home to a studio tour based around the franchise.
Certainly even if such an incident were to impact the production schedule of The Witches it wouldn’t have been by very much.
Even the tour was not affected by the incident, so it appears that while the attack did take place, everything else was exaggerated.
However, it seems that in the end the movie has moved forward without so much as noticing that anything happened.