Run on_item_use CSM callback even if item is not marked usable

Mods may want to to handle item interaction even if the item
is not marked usable (= server-side callback exists).

clientmods/preview/init.lua

@@ -66,6 +66,10 @@ core.register_on_item_use(function(itemstack, pointed_thing)
 	print("pointed_thing :" .. dump(pointed_thing))
 	print("item = " .. itemstack:get_name())
 
+	if not itemstack:is_empty() then
+		return false
+	end
+
 	local pos = vector.add(core.localplayer:get_pos(), core.camera:get_offset())
 	local pos2 = vector.add(pos, vector.multiply(core.camera:get_look_dir(), 100))
 

src/client/game.cpp

@@ -3061,6 +3061,9 @@ void Game::processPlayerInteraction(f32 dtime, bool show_hud, bool show_debug)
 	} else if (input->getLeftState()) {
 		// When button is held down in air, show continuous animation
 		runData.left_punch = true;
+		// Run callback even though item is not usable
+		if (input->getLeftClicked() && client->modsLoaded())
+			client->getScript()->on_item_use(selected_item, pointed);
 	} else if (input->getRightClicked()) {
 		handlePointingAtNothing(selected_item);
 	}