Dima Kravchyna

Fixed Null Reference exception, conversion hangs and merged with the main branch

3

This commit has fixed Null Reference bugs, fixed conversion hangs and other improvements from the main branch

Open CASCADE Technology 7.5.0 support

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Would you upgrade OCC lib to[ 7.5.0 ](https://old.opencascade.com/sites/default/files/documents/release_notes_7.5.0.pdf) ?

I've double-checked properties and here is the updated pull request. Could you @artrmz, please, create a new preview package with this Null Safety implementation?