Restrict the radius to 20

If it is any larger, it would cause a server to crash.

plugin/src/main/java/com/lishid/openinv/commands/SearchContainerCommand.java

@@ -72,6 +72,10 @@ public class SearchContainerCommand implements TabExecutor {
             }
         }
         
+        if (radius > 20) {
+            radius = 20;
+        }
+
         Player senderPlayer = (Player) sender;
         World world = senderPlayer.getWorld();
         Chunk centerChunk = senderPlayer.getLocation().getChunk();