Fix exception when opening map
Fix exception when opening map

A dialog is not a window instance.
This issue only occured with $wgKartographerStaticMapframe = false

Bug: T251218
Change-Id: I0400bbe2defbc9f41b921b5b823438811b7023f1

wikimedia/mediawiki-extensions-Kartographer,wikimedia/mediawiki-extensions-Kartographer,wikimedia/mediawiki-extensions-Kartographer