Getting errors with null fields

In Microsoft Power Automate, when you create a flow, here is what could happen with null field that cause trouble:

1. You may be expecting wrong behavior when perform an action with null field.
2. If you are not handling null fields correctly, you may be expecting runtime errors like:
   • InvalidTemplate. Unable to process template language expressions. The provided value is of type 'Null'.

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1. If a flow runs with a null field, it will cause:
   • Wrong behavior: flow action's input is receiving null field, when it expects a different value.
2. Use expression towards null fields. It will cause:
   • Runtime error: expression expects its parameter to be a string, an object or an array but receives null. 

You can set up a condition check for null field. Here is the steps to create a condition check for null.

1. Add a new condition action.

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2. Choose dynamic content output (e.g. user email) you want to check.

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3. Set the operation to be (e.g.) "is not equal to".

4. Put the value field as the expression value "null".

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You can also use coalesce function to provide default values when a value is null. For example, using coalesce(trigger().outputs, '') will default to empty string when trigger().outputs is null.

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Note: If you are still getting a runtime error, it may be caused by reference null properties in an object. You should use the question mark operator "?". For example, to handle null outputs from a trigger, you can use this expression:

@coalesce(trigger().outputs?.body?.<someProperty>, '<property-default-value>').

See Coalesce function, Operators for more information.