Do you know exactly what assertions are and what they are used for?
An example of the use of assertions is to check pre- and postconditions in parts of your code. A method may for example have an assert to check that the parameters that were passed to it are valid.
If an AssertionError happens in your application, it means that there is a bug somewhere in your software. You might be passing invalid arguments to a method somewhere, or you're doing something else so that the software gets into an undefined, invalid state.
AssertionErrors should NEVER happen in production software. If an AssertionError happens, it means that something is seriously wrong in your software and
you should debug it.