It doesn't show it on this diagram but the main injection relay (item 28) has a diode inside it for just that happening.
It won't turn on and power up the ECU if the battery is backwards, they used to call it the Safety Diode on earlier fuel injected bikes[You must be registered and logged in to see this link.]
You can see it on this Norge schematic, its a similar bike. Item (29)[You must be registered and logged in to see this link.]
I think its a bit silly using a special relay, the diode should be outside between the socket and chassis like they had on earlier bikes, then you could have all the same relay.
This pre 2000 for example. Item (48)[You must be registered and logged in to see this link.]
Even earlier they had the diode inside the P8 ECU, I replaced a couple of those when the owner accidentally fried it somehow.