WM_TRANSIENT_FOR(WINDOW): window id # ... property gone after updating to 4.20.3-1

I'm using ArchBTW. Updated from 4.20.2-1 to 4.20.3-1 and now child windows/dialogs such as "rename" are no longer detected by my WM and proper placement is not working, most probably because now the WM_TRANSIENT_FOR(WINDOW) property is missing when looked at with xprop. (dowgrading solves it)

Regression introduced by commit: 464af7bd

Reproducer:

• open thunar window
• press F2 on some file
• open some terminal and execute xprop | grep WM_TRANSIENT_FOR
• Alt/Tab until you see the renamer dialog
• click on the rename dialog.

Expected Outcome:

WM_TRANSIENT_FOR(WINDOW): window id # <some random value>

Actual Outcome:

No output