Don't call next suggestion provider if there are no args left.

worldedit-core/src/main/java/com/sk89q/worldedit/util/command/composition/SimpleCommand.java

@@ -43,6 +43,11 @@ public final List<String> getSuggestions(CommandArgs args, CommandLocals locals)
                     throw e;
                 }
             }
+
+            // There's nothing more anyway
+            if (args.position() == args.size()) {
+                return suggestions;
+            }
         }
         return suggestions;
     }