Fix image sources not being marked as loaded on error

[tzetter]

Launch Checklist

This fixes image sources not being marked as loaded when loading of the image fails.

This behavior changed as a result of 859b1a7#diff-d4cf28d025bceded1ecd0f4b0b3095b831e34317b61f25611d3cf44e82d64c14 as the new try/catch approach doesn't change the _loaded variable on error.

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• Link to related issues.
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• Write tests for all new functionality.
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• Add an entry to CHANGELOG.md under the ## main section.

[HarelM]

Thanks!!