450983 PSD: don't attempt to read zero-sized blocks
Test Plan
Load Tiar's PSD demo file, check that it doesn't fail except on the "Additional Layer Information" part of the parsing (because that part of the file doesn't have a boundary--see the standard).
Formalities Checklist
-
I confirmed this builds. -
I confirmed Krita ran and the relevant functions work. -
I tested the relevant unit tests and can confirm they are not broken. (If not possible, don't hesitate to ask for help!) -
I made sure my commits build individually and have good descriptions as per KDE guidelines. -
I made sure my code conforms to the standards set in the HACKING file. -
I can confirm the code is licensed and attributed appropriately, and that unattributed code is mine, as per KDE Licensing Policy.