Fire stops ticking forever if gamerule doFireTick is set to false once

The bug

If the gamerule doFireTick is set to false, existing fire blocks will continue to not tick even if that gamerule is set back to true, and as such don't go out or spread to other blocks.

To reproduce

1. /gamerule doFireTick false
2. Place fire
3. /gamerule doFireTick true
4. Wait
   → The fire never goes out or spreads to other blocks