Gracefully handle the absence of WorldBorder

Additionally move `isOutsideWorldBorder` to FLocation, because it
doesn't belong in Board/MemoryBoard.

src/main/java/com/massivecraft/factions/Board.java

@@ -45,9 +45,6 @@ public abstract class Board {
     // Is this coord connected to any coord claimed by the specified faction?
     public abstract boolean isConnectedLocation(FLocation flocation, Faction faction);
 
-    // Is this location outside the world border? 
-    public abstract boolean isOutsideWorldBorder(FLocation flocation, int buffer);
-    
     public abstract boolean hasFactionWithin(FLocation flocation, Faction faction, int radius);
 
     //----------------------------------------------//

src/main/java/com/massivecraft/factions/FLocation.java

@@ -1,10 +1,7 @@
 package com.massivecraft.factions;
 
 import com.massivecraft.factions.util.MiscUtil;
-import org.bukkit.Bukkit;
+import org.bukkit.*;
-import org.bukkit.Chunk;
-import org.bukkit.Location;
-import org.bukkit.World;
 import org.bukkit.block.Block;
 import org.bukkit.entity.Player;
 
@@ -15,10 +12,21 @@ import java.util.Set;
 
 public class FLocation implements Serializable {
     private static final long serialVersionUID = -8292915234027387983L;
+    private static final boolean worldBorderSupport;
     private String worldName = "world";
     private int x = 0;
     private int z = 0;
 
+    static {
+        boolean worldBorderClassPresent = false;
+        try {
+            Class.forName("org.bukkit.WorldBorder");
+            worldBorderClassPresent = true;
+        } catch (ClassNotFoundException ignored) {}
+
+        worldBorderSupport = worldBorderClassPresent;
+    }
+
     //----------------------------------------------//
     // Constructors
     //----------------------------------------------//
@@ -158,6 +166,26 @@ public class FLocation implements Serializable {
         return loc.getWorld().getName().equalsIgnoreCase(getWorldName()) && chunk.getX() == x && chunk.getZ() == z;
     }
 
+    /**
+     * Checks if the chunk represented by this FLocation is outside the world border
+     *
+     * @param buffer the number of chunks from the border that will be treated as "outside"
+     * @return whether this location is outside of the border
+     */
+    public boolean isOutsideWorldBorder(int buffer) {
+        if (!worldBorderSupport) {
+            return false;
+        }
+
+        WorldBorder border = getWorld().getWorldBorder();
+        Chunk chunk = border.getCenter().getChunk();
+
+        int lim = FLocation.chunkToRegion((int) border.getSize()) - buffer;
+        int diffX = Math.abs(chunk.getX() - x);
+        int diffZ = Math.abs(chunk.getZ() - z);
+        return diffX > lim || diffZ > lim;
+    }
+
     //----------------------------------------------//
     // Some Geometry
     //----------------------------------------------//

src/main/java/com/massivecraft/factions/zcore/persist/MemoryBoard.java

@@ -4,11 +4,7 @@ import com.massivecraft.factions.*;
 import com.massivecraft.factions.struct.Relation;
 import com.massivecraft.factions.util.AsciiCompass;
 import com.massivecraft.factions.util.LazyLocation;
-
 import org.bukkit.ChatColor;
-import org.bukkit.Chunk;
-import org.bukkit.World;
-import org.bukkit.WorldBorder;
 
 import java.util.ArrayList;
 import java.util.HashMap;
@@ -128,21 +124,6 @@ public abstract class MemoryBoard extends Board {
         }
         return false;
     }
-    
-    /**
-     * Checks if a claim chunk is outside the world border
-     * @param flocation claim chunk
-     * @return if claim chunk is outside world border
-     */
-    public boolean isOutsideWorldBorder(FLocation flocation, int buffer) {
-        World world = flocation.getWorld();
-        WorldBorder border = world.getWorldBorder();
-        Chunk chunk = border.getCenter().getChunk();
-        int lim = FLocation.chunkToRegion((int) border.getSize()) - buffer;
-        int diffX = (int) Math.abs(chunk.getX() - flocation.getX());
-        int diffZ = (int) Math.abs(chunk.getZ() - flocation.getZ());
-        return diffX > lim || diffZ > lim;
-    }
 
     /**
      * Checks if the faction at the flocation is not wilderness and different than given faction.

src/main/java/com/massivecraft/factions/zcore/persist/MemoryFPlayer.java

@@ -698,7 +698,7 @@ public abstract class MemoryFPlayer implements FPlayer {
             }
         } else if (factionBuffer > 0 && Board.getInstance().hasFactionWithin(flocation, myFaction, factionBuffer)) {
             error = P.p.txt.parse(TL.CLAIM_TOOCLOSETOOTHERFACTION.format(factionBuffer));
-        } else if (Board.getInstance().isOutsideWorldBorder(flocation, worldBuffer)) {
+        } else if (flocation.isOutsideWorldBorder(worldBuffer)) {
             if(worldBuffer > 0) {
                 error = P.p.txt.parse(TL.CLAIM_OUTSIDEBORDERBUFFER.format(worldBuffer));                 
             } else {