SUMMARY
In Krita 5.2, transform masks use `dumbparams` until they're first edited. The parser for those params was moved into a separate library in commit d1cc758, meaning any files that contain `dumbparams` transform masks fail to load.

STEPS TO REPRODUCE
1. Launch Krita 5.2.2
2. Create a new document
3. Add a transform mask to the background layer
4. Save the file
5. Launch Krita 5.3.0-prealpha (git 17e5603)
6. Try to open the file

OBSERVED RESULT
Krita fails to load the image, complaining it "Could not create transform mask params"

EXPECTED RESULT
The file should open successfully

SOFTWARE/OS VERSIONS
Krita: 5.3.0-prealpha (git 17e5603)

ADDITIONAL INFORMATION
You can observe the param type changing using this script:
    doc = Krita.instance().activeDocument()
    print(doc.activeNode().toXML())

1. Launch Krita
2. Create a new document
3. Add a transform mask to the background layer
4. Run the script
5. Start editing the mask
6. Run the script again

In 5.2, the mask starts out using `dumbparams`, then moves to `tooltransformparams` when you edit the transform. If you perform those same steps in 5.3 the transform mask immediately uses `tooltransformparams`.