Spawn_entity causes Minecraft to crash when min and max_wait_time is the same

Release_466466

Summary:
When setting min_wait_time and max_wait_time to the same value, Minecraft crashes

Impact:
Sometimes not having variance between spawning is important. For example:

• We are using interact to spawn an entity to trigger a redstone mechanic. Having a variance (0,1) feels bad for the player because there's no instant feedback (0,0 would be preferred)
• In one of our maps, we are having entity A spawn entity B to have entity B ride entity A as a pseudo team. The variance makes the mechanic a bit inconsistent.

Repro Steps:

1. Load included JSON into world
2. Summon Zombie
3. Game crashes

Observed Results:
Game crashes with the following error in the debug_log
```
[992:8124] - ERROR SYSTEM Assertion failed: Can't generate a number in [0,0)
Condition is false: n > 0
```

Expected Results:
Zombie spawns, then spawns a ocelot 1 second later

Screenshots/videos attached:
n/a