Fix for omnious reagent transfer error in #1673

If your glass is empty get_master_reagent_id() will return null and proc will try to add 5 units of null to glass
Took me half a hour of guessing and then one minute of testing after changing WARNING to CRASH
Lesson for future generations - 1 message with chain of calls is better than 1000 of the most elaborate of warnings, use crash for your own good kids
Fixes  #1673