Noticed the issue with following:

• When placing tnt blocks, (they are blocked on the server) and crashed the server.

java.lang.Error
at net.minecraft.server.v1_8_R1.World.getType(World.java:655)
at net.minecraft.server.v1_8_R1.Explosion.a(Explosion.java:76)
at net.minecraft.server.v1_8_R1.World.createExplosion(World.java:1626)
at net.minecraft.server.v1_8_R1.WorldServer.createExplosion(WorldServer.java:965)
at net.minecraft.server.v1_8_R1.EntityTNTPrimed.explode(EntityTNTPrimed.java:83)
at net.minecraft.server.v1_8_R1.EntityTNTPrimed.s_(EntityTNTPrimed.java:62)
at net.minecraft.server.v1_8_R1.World.entityJoinedWorld(World.java:1374)
at net.minecraft.server.v1_8_R1.World.g(World.java:1352)
at net.minecraft.server.v1_8_R1.World.tickEntities(World.java:1222)
at net.minecraft.server.v1_8_R1.WorldServer.tickEntities(WorldServer.java:539)
at net.minecraft.server.v1_8_R1.MinecraftServer.z(MinecraftServer.java:700)
at net.minecraft.server.v1_8_R1.DedicatedServer.z(DedicatedServer.java:284)
at net.minecraft.server.v1_8_R1.MinecraftServer.y(MinecraftServer.java:598)
at net.minecraft.server.v1_8_R1.MinecraftServer.run(MinecraftServer.java:506)
at java.lang.Thread.run(Unknown Source)