NavigationServer: Restore constness for thread safe `get_singleton`

This was removed by mistake in #47024, NavigationServer uses internal
mutability for thread safety, and removing `const` breaks the contract.

4 files changed, 4 insertions, 4 deletions

diff --git a/servers/navigation_server_2d.cpp b/servers/navigation_server_2d.cpp
index c4c10ebf3b..53190d7681 100644
--- a/servers/navigation_server_2d.cpp
+++ b/servers/navigation_server_2d.cpp
@@ -204,7 +204,7 @@ void NavigationServer2D::_bind_methods() {
 NavigationServer2D::NavigationServer2D() {
 	singleton = this;
 	ERR_FAIL_COND_MSG(!NavigationServer3D::get_singleton(), "The Navigation3D singleton should be initialized before the 2D one.");
-	NavigationServer3D::get_singleton()->connect("map_changed", callable_mp(this, &NavigationServer2D::_emit_map_changed));
+	NavigationServer3D::get_singleton_mut()->connect("map_changed", callable_mp(this, &NavigationServer2D::_emit_map_changed));
 }
 
 NavigationServer2D::~NavigationServer2D() {
diff --git a/servers/navigation_server_2d.h b/servers/navigation_server_2d.h
index 8ab479b8fd..2dd718e09c 100644
--- a/servers/navigation_server_2d.h
+++ b/servers/navigation_server_2d.h
@@ -52,7 +52,7 @@ protected:
 
 public:
 	/// Thread safe, can be used across many threads.
-	static NavigationServer2D *get_singleton() { return singleton; }
+	static const NavigationServer2D *get_singleton() { return singleton; }
 
 	/// MUST be used in single thread!
 	static NavigationServer2D *get_singleton_mut() { return singleton; }
diff --git a/servers/navigation_server_3d.cpp b/servers/navigation_server_3d.cpp
index 03c75369a6..d78e58bea0 100644
--- a/servers/navigation_server_3d.cpp
+++ b/servers/navigation_server_3d.cpp
@@ -84,7 +84,7 @@ void NavigationServer3D::_bind_methods() {
 	ADD_SIGNAL(MethodInfo("map_changed", PropertyInfo(Variant::RID, "map")));
 }
 
-NavigationServer3D *NavigationServer3D::get_singleton() {
+const NavigationServer3D *NavigationServer3D::get_singleton() {
 	return singleton;
 }
 
diff --git a/servers/navigation_server_3d.h b/servers/navigation_server_3d.h
index c70d87ec16..f711e4e0e5 100644
--- a/servers/navigation_server_3d.h
+++ b/servers/navigation_server_3d.h
@@ -55,7 +55,7 @@ protected:
 
 public:
 	/// Thread safe, can be used across many threads.
-	static NavigationServer3D *get_singleton();
+	static const NavigationServer3D *get_singleton();
 
 	/// MUST be used in single thread!
 	static NavigationServer3D *get_singleton_mut();