Crash closing document with Filter Editors dialog floating

Steps to reproduce:

• Open Inkscape
• Draw a rectangle
• Apply Filter > Fill and Transparency > Fast Crop
• Keep rectangle selected
• Open a new (Inkscape) window and repeat
• Open the Filter Editor Dialog
• Make sure the dialog is floating (default in 1.2-dev)
• Switch to the first Inkscape window
• Close window (without saving)
• Click on the last Inkscape window

What happened?

• Crash inkscape_backtrace_filter_dialog_close_window.txt

What should have happened?

• No crash

Sample attachments: backtrace inkscape_backtrace_filter_dialog_close_window.txt

Version info

• Inkscape 1.2-dev (6a387c76, 2021-08-16) Linux Mint 20
• Inkscape 1.1 (22cf7852, 2021-08-02) Linux Mint 20

Not replicated Inkscape 1.0.x (f38d80df, 2021-05-16) Linux Mint 20

Appears to be introduced in dialog rewrite (c2d0ea12)