Have factions return as 0 instead of null.

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

@@ -97,7 +97,7 @@ public abstract class MemoryFPlayer implements FPlayer {
 
     public Faction getFaction() {
         if (this.factionId == null) {
-            return null;
+            this.factionId = "0";
         }
         return Factions.getInstance().getFactionById(this.factionId);
     }