Move Godot Physics 2D into a module; add dummy 2D physics server

If the module is enabled (default), 2D physics works as it did before.

If the module is disabled and no other 2D physics server is registered
(via a module or GDExtension), then we fall back to a dummy
implementation which effectively disables 2D physics functionality (and
a warning is printed).

The dummy 2D physics server can also be selected explicitly, in which
case no warning is printed.

1 files changed, 3 insertions, 1 deletions

diff --git a/servers/physics_server_2d.cpp b/servers/physics_server_2d.cpp
index da25621ba5..f4f9a2e8b7 100644
--- a/servers/physics_server_2d.cpp
+++ b/servers/physics_server_2d.cpp
@@ -972,7 +972,9 @@ String PhysicsServer2DManager::get_server_name(int p_id) {
 }
 
 PhysicsServer2D *PhysicsServer2DManager::new_default_server() {
-	ERR_FAIL_COND_V(default_server_id == -1, nullptr);
+	if (default_server_id == -1) {
+		return nullptr;
+	}
 	Variant ret;
 	Callable::CallError ce;
 	physics_2d_servers[default_server_id].create_callback.callp(nullptr, 0, ret, ce);