Added clearRegisters() so that when another file is selected from the GUI, all register displays are cleared to avoid confusion.
Added additional if-statement block to write() method; if data parameter is null, this indicates the register is being cleared for the benefit of the GUI, and this parameter being null will cause an exeception if not handled properly. Thus, the data field is set to an empty String to be passed to the ModuleUpdateEvent. Works correctly.
Selecting a new assembly file to open now clears the interface fields of any old data for clarity.