![Custom Function returns NULL value when run in Field Calculator (Preview works fine) · Issue #41695 · qgis/QGIS · GitHub Custom Function returns NULL value when run in Field Calculator (Preview works fine) · Issue #41695 · qgis/QGIS · GitHub](https://user-images.githubusercontent.com/87969978/133457170-a834a12d-fe75-4744-9586-ded78934039c.jpg)
Custom Function returns NULL value when run in Field Calculator (Preview works fine) · Issue #41695 · qgis/QGIS · GitHub
![Custom Function returns NULL value when run in Field Calculator (Preview works fine) · Issue #41695 · qgis/QGIS · GitHub Custom Function returns NULL value when run in Field Calculator (Preview works fine) · Issue #41695 · qgis/QGIS · GitHub](https://user-images.githubusercontent.com/16478283/108544391-0b768900-72ef-11eb-887a-3b73aa12a7f9.png)
Custom Function returns NULL value when run in Field Calculator (Preview works fine) · Issue #41695 · qgis/QGIS · GitHub
Custom Function returns NULL value when run in Field Calculator (Preview works fine) · Issue #41695 · qgis/QGIS · GitHub
![qgis - NULL values when using overlay_within function in Field Calculator - Geographic Information Systems Stack Exchange qgis - NULL values when using overlay_within function in Field Calculator - Geographic Information Systems Stack Exchange](https://i.stack.imgur.com/tpc0L.png)
qgis - NULL values when using overlay_within function in Field Calculator - Geographic Information Systems Stack Exchange
![New values created with QGIS field calculator become null upon saving - Geographic Information Systems Stack Exchange New values created with QGIS field calculator become null upon saving - Geographic Information Systems Stack Exchange](https://i.stack.imgur.com/TET04.png)
New values created with QGIS field calculator become null upon saving - Geographic Information Systems Stack Exchange
![coordinate system - $area gives NULL for some polygons in QGIS's Field Calculator - Geographic Information Systems Stack Exchange coordinate system - $area gives NULL for some polygons in QGIS's Field Calculator - Geographic Information Systems Stack Exchange](https://i.stack.imgur.com/ZSc3g.png)
coordinate system - $area gives NULL for some polygons in QGIS's Field Calculator - Geographic Information Systems Stack Exchange
![qgis - NULL values when using overlay_within function in Field Calculator - Geographic Information Systems Stack Exchange qgis - NULL values when using overlay_within function in Field Calculator - Geographic Information Systems Stack Exchange](https://i.stack.imgur.com/Uo4za.png)