Don't let Player#getLocale return null

Thanks for reporting @MatrixTunnel

Spigot-Server-Patches/Implement-PlayerLocaleChangeEvent.patch

@@ -5,7 +5,7 @@ Subject: [PATCH] Implement PlayerLocaleChangeEvent
 
 
 diff --git a/src/main/java/net/minecraft/server/EntityPlayer.java b/src/main/java/net/minecraft/server/EntityPlayer.java
-index ccd4cabcd..6271d28a2 100644
+index e9377ca3..15a448d7 100644
 --- a/src/main/java/net/minecraft/server/EntityPlayer.java
 +++ b/src/main/java/net/minecraft/server/EntityPlayer.java
 @@ -0,0 +0,0 @@ import org.bukkit.inventory.MainHand;
@@ -45,17 +45,28 @@ index ccd4cabcd..6271d28a2 100644
          this.cm = packetplayinsettings.d();
          this.getDataWatcher().set(EntityPlayer.br, Byte.valueOf((byte) packetplayinsettings.e()));
 diff --git a/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java b/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
-index 17a14fdc0..b65ac0c7e 100644
+index 17a14fdc..41330c2a 100644
 --- a/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
 +++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
+@@ -0,0 +0,0 @@ public class CraftPlayer extends CraftHumanEntity implements Player {
+ 
+     @Override
+     public String getLocale() {
+-        return getHandle().locale;
+-
++        // Paper start - Locale change event
++        final String locale = getHandle().locale;
++        return locale != null ? locale : "en_us";
++        // Paper end
+     }
+ 
+     public void setAffectsSpawning(boolean affects) {
 @@ -0,0 +0,0 @@ public class CraftPlayer extends CraftHumanEntity implements Player {
          @Override
          public String getLocale()
          {
 -           return getHandle().locale;
-+            // Paper start - Locale change event
-+            final String locale = getHandle().locale;
-+            return locale != null ? locale : "en_us";
++            return CraftPlayer.this.getLocale(); // Paper
          }
  
          @Override