Fix icon scaling for non .svg icons

[ralphwetzel]

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)

Proposed changes

In case a contrib node uses an oversized icon in non-.svg format, the size of this icon might change when pulling the node from the palette to the editor view:

This PR modifies the scaling algorithm - for that particular case - to ensure the size of the icon stays as it is in the palette:

Fix for #4490.

Checklist

• I have read the contribution guidelines
• For non-bugfix PRs, I have discussed this change on the forum/slack team.
• I have run npm run test to verify the unit tests pass
• I have added suitable unit tests to cover the new/changed functionality