extractValueFromColumn should respect custom ValueProvider return value, even if null #182
Description
Describe the bug
Currently, if a custom ValueProvider is defined for a column (by calling gridExporter.setExportValue(...)) but returns null, extractValueFromColumn(...) continues trying to obtain a value from other sources (e.g. bean properties or renderers).
This prevents intentional null values used, for example, to export a blank cell in Excel from being respected.
Expected behavior
If a custom ValueProvider is present, its result should be used as is, even if it is null. The method should not fall back to other value sources.
Minimal reproducible example
No response
Add-on Version
2.5.2
Vaadin Version
24.6.6
Additional information
No response