error

01:28:08 [WARNING] [Quester] Task #39 for Quester v0.7.0-SNAPSHOT generated an exception
java.lang.IllegalArgumentException: Cannot measure distance between Housing and Housing
        at org.bukkit.Location.distanceSquared(Location.java:381)
        at com.gmail.molnardad.quester.listeners.PositionListener.run(PositionListener.java:66)
        at org.bukkit.craftbukkit.v1_4_R1.scheduler.CraftTask.run(CraftTask.java:53)
        at org.bukkit.craftbukkit.v1_4_R1.scheduler.CraftScheduler.mainThreadHeartbeat(CraftScheduler.java:344)
        at net.minecraft.server.v1_4_R1.MinecraftServer.r(MinecraftServer.java:530)
        at net.minecraft.server.v1_4_R1.DedicatedServer.r(DedicatedServer.java:224)
        at net.minecraft.server.v1_4_R1.MinecraftServer.q(MinecraftServer.java:494)
        at net.minecraft.server.v1_4_R1.MinecraftServer.run(MinecraftServer.java:427)
        at net.minecraft.server.v1_4_R1.ThreadServerApplication.run(SourceFile:849)