When you create a SmartObject based on a SalesForce (legacy) service instance, you are unable to use a NULL filter on a SmartObject property in K2 smartforms.
- Ensure you have K2 Five (5.1) installed.
- Download the K2 Five (5.1) FP22 from K2 Partner and Customer Portal.
- Install the K2 Five (5.1) FP22 to apply the fix.
- It is recommended to refresh the browser cache.
- It might be necessary to cache the SalesForce credentials again.