Exception Handling is preparing the program for alternate scenarios than the one expected. It allows for more robust solutions and is a common technique across languages.
Although exception handling is traditionally reactive, capturing an exception after it occurs, the same principles can be applied in a proactive measure.
For example, if a code block relies on an instance being identified, you can try assuming the instance exists, and then reactively catch the exception, or you can proactively ensure the instance exists before trying the code block. Either way, the developer is aware of the potential exception beforehand, and therefore programming in a way to account for it.
This is the practice of verifying assumptions before you rely on them, often via a conditional before the code block.
Relevant GameMaker syntax includes:
instance_exists
is_undefined
This is the practice of surronding the code block reliant on the assumption in a try / catch statement. Learn more here.
When should one use proactive exception handling?
GeeksForGeeks - Exception Handling in Programming
Stack Overflow - When to use try/catch blocks