Check if GL manager exist to prevent crash when using multithreaded renderer with Vulkan.

platform/linuxbsd/display_server_x11.cpp

@@ -4175,13 +4175,17 @@ void DisplayServerX11::process_events() {
 
 void DisplayServerX11::release_rendering_thread() {
 #if defined(GLES3_ENABLED)
-	gl_manager->release_current();
+	if (gl_manager) {
+		gl_manager->release_current();
+	}
 #endif
 }
 
 void DisplayServerX11::make_rendering_thread() {
 #if defined(GLES3_ENABLED)
-	gl_manager->make_current();
+	if (gl_manager) {
+		gl_manager->make_current();
+	}
 #endif
 }
 

platform/osx/display_server_osx.mm

@@ -2920,7 +2920,9 @@ void DisplayServerOSX::make_rendering_thread() {
 
 void DisplayServerOSX::swap_buffers() {
 #if defined(GLES3_ENABLED)
-	gl_manager->swap_buffers();
+	if (gl_manager) {
+		gl_manager->swap_buffers();
+	}
 #endif
 }
 

platform/windows/display_server_windows.cpp

@@ -656,7 +656,9 @@ void DisplayServerWindows::delete_sub_window(WindowID p_window) {
 
 void DisplayServerWindows::gl_window_make_current(DisplayServer::WindowID p_window_id) {
 #if defined(GLES3_ENABLED)
-	gl_manager->window_make_current(p_window_id);
+	if (gl_manager) {
+		gl_manager->window_make_current(p_window_id);
+	}
 #endif
 }