What does "trying to access the 'id' property on a null value" mean?

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This error message indicates that you are trying to access the property 'id' of a variable that has a value of null. In other words, the variable doesn't exist or hasn't been initialized yet. It could be due to a mistake in your code where you're trying to access a variable before it's been defined or initialized. To fix this error, ensure that the object or variable you're trying to access exists before you try to use it.