Compared to the original it has the following advantages:
Avoids validating slots that wont be used. i.e.:

you validate slot1 and slot2 but then just replace it:

if (slot1) {
 +                verifySlotExists(slot1);
 +              }
 +              if (slot2) {
 +                verifySlotExists(slot2);
 +              }
 +
 +              slot1 = slots[0];
 +              slot2 = slots[1];

So the validation serves no purpose.