Pass empty value to Person field in SharePoint List

[jsangerman]

I am using a Form to collect data and then passing the results to a SharePoint list. The form is used for user support and to gather multiple uses. If the responder says the ticket is for access, they see question 4 and can decide whether the access is for themself or someone else. The latter shows them question 5.

Because the input is variable, I am using a condition to populate a variable with the input to my SharePoint list. If the request is not for access, that variable (AccessUser) will have 0 length when passed to the SharePoint list. That is leading to an error:

The specified user could not be found.
clientRequestId: 10902738-6902-42f0-ad97-df5d054a2f76
serviceRequestId: 10902738-6902-42f0-ad97-df5d054a2f76

Here's a portion of the flow that I need to function properly. How can I conditionally pass no user ID to a person column in a SharePoint List?

I prefer not to use a Condition to have conditional Create Item actions. I'd prefer to use conditions to populate variables that are then passed through a single Create Item action.

[PrasadAthalye]

You can build a null check expression in the claims mapping. 

if(equals(variables('Accessuser'), null), null,variables('Accessuser'))

[jsangerman]

I added that, but am still getting the same error.

It seems to not like a null value for a person. Which is strange because if I leave that column blank in the action, it works fine. So nothing = success but null = error

[jsangerman]

Here's the input to that action.

[PrasadAthalye]

This seems to be a limitation of Update Item action that you can not pass empty or null value. Refer following thread.

https://powerusers.microsoft.com/t5/General-Power-Automate/How-to-clear-SharePoint-quot-Person-or-gr...

You can use REST API call to update the item where you can implement null check.

[paypal_matt]

I was originally having the same error with Prasad's solution

if(empty(variables('Accessuser'), null, variables('Accessuser'))

where the value would still enter as an empty string "" instead of null in the input. But then I tried switching to the old designer by toggling the switch in the upper right and I discovered the source of the problem. When you're in the old designer mode, there's an option to "Peek code". When I view the Create Item action in this mode, I see the if statement above is passed as a variable like this in the backend code:

@{if(empty(variables('Accessuser'), null, variables('Accessuser'))}

 However, if you edit the expression in the old editor, then the variable in the backend code changes to:

@if(empty(variables('Accessuser'), null, variables('Accessuser'))

Notice the miniscule difference here of curly braces { } around the first variable and not in the second. When the first is submitted in the Create Item action, it gets converted to an empty string as it is essentially an Array object containing only nulls (nothing). But the second gets converted to the actual value null as expected. Not sure why this functionality changes between the old designer and new designer but hopefully this helps someone else with the same problem in the future.

[cardotdev]

Just experienced the following behavior on one flow, but following the same steps failed on another flow, where the specified user @null could not be found:

Inputting a custom value directly in Create / Update Item Sharepoint actions will accept the function null. It will not be accepted however if you put the function null in a variable and then try to pass that null variable to the column. 
Instead, if you need to pass a blank variable to a person column, set value to "@null" without quotations in a string variable. 

Edit: No idea why but this worked for the flow that would not accept @null from the variable: Solved: Re: How can I clear a Sharepoint list Hyperlink co... - Power Platform Community (microsoft....