SPIGOT-3192: Return default value for invalid map icons

By: md_5 <git@md-5.net>

paper-server/nms-patches/MapIcon.patch

@@ -0,0 +1,11 @@
+--- a/net/minecraft/server/MapIcon.java
++++ b/net/minecraft/server/MapIcon.java
+@@ -86,7 +86,7 @@
+         }
+ 
+         public static MapIcon.Type a(byte b0) {
+-            return values()[b0];
++            return b0 >= 0 && b0 < values().length ? values()[b0] : MapIcon.Type.PLAYER; // CraftBukkit
+         }
+     }
+ }