TYPO3 Core

When getting an icon with the overlay parameter containing an empty string, the API considers the parameter is filled and returns the "not found icon".

The best example is this Fluid snippet:

<core:icon identifier="tx-my-icon" 
           overlay="{f:if(condition: myCondition, then: 'my-overlay-icon')}" />

When the condition myCondition is false, the "not found icon" is added as an overlay, but no overlay should be added at all.