For a situation like this it would be nice if the debugger could provide you with a list of warnings when a situation like this arose. For example "Warning: this operation has no object instance".
I think the Construct Classic debugger did something like this, but it wasn't especially useful. In a long event sheet the "zero instances action" can happen several times per tick for innocuous reasons, and that ends up spamming the log with huge amounts of irrelevant data, making it hard to pick out the cases where it really is a problem.