Upstream has released updates that appears to apply and compile correctly.
This update has not been tested by PaperMC and as with ANY update, please do your own testing
Bukkit Changes:
0399d9d6 SPIGOT-5341: Add Material.isAir
547f5709 SPIGOT-5353: Expand explosion API by adding source entity
CraftBukkit Changes:
7deb3728 SPIGOT-5309: Call cancelled EntityDamageEvent when damaging invisible armor stands
46351e17 SPIGOT-5341: Add Material.isAir
683bae06 SPIGOT-5342: Lore lost when deserializing items with no version stored
c2d12011 SPIGOT-5353: Expand explosion API by adding source entity
