Add nicer error when using player commands as console.

Also fix slash counts for Bukkit.

worldedit-bukkit/src/main/java/com/sk89q/worldedit/bukkit/WorldEditPlugin.java

@@ -289,7 +289,7 @@ public class WorldEditPlugin extends JavaPlugin implements TabCompleter {
         // code of WorldEdit expects it
         String[] split = new String[args.length + 1];
         System.arraycopy(args, 0, split, 1, args.length);
-        split[0] = cmd.getName();
+        split[0] = "/" + cmd.getName();
 
         CommandEvent event = new CommandEvent(wrapCommandSender(sender), Joiner.on(" ").join(split));
         getWorldEdit().getEventBus().post(event);
@@ -303,7 +303,7 @@ public class WorldEditPlugin extends JavaPlugin implements TabCompleter {
         // code of WorldEdit expects it
         String[] split = new String[args.length + 1];
         System.arraycopy(args, 0, split, 1, args.length);
-        split[0] = cmd.getName();
+        split[0] = "/" + cmd.getName();
 
         CommandSuggestionEvent event = new CommandSuggestionEvent(wrapCommandSender(sender), Joiner.on(" ").join(split));
         getWorldEdit().getEventBus().post(event);

worldedit-core/src/main/java/com/sk89q/worldedit/extension/platform/PlatformCommandManager.java

@@ -469,6 +469,10 @@ public final class PlatformCommandManager {
         store.injectValue(Key.of(Actor.class), ValueProvider.constant(actor));
         if (actor instanceof Player) {
             store.injectValue(Key.of(Player.class), ValueProvider.constant((Player) actor));
+        } else {
+            store.injectValue(Key.of(Player.class), context -> {
+                throw new CommandException(TextComponent.of("This command must be used with a player."), ImmutableList.of());
+            });
         }
         store.injectValue(Key.of(Arguments.class), ValueProvider.constant(event::getArguments));
         store.injectValue(Key.of(LocalSession.class),