GDScript: Improve call analysis

* Add missing `UNSAFE_CALL_ARGUMENT` warning.
* Fix `Object` constructor.
* Display an error for non-existent static methods.

modules/gdscript/tests/scripts/analyzer/features/null_initializer.gd

@@ -6,10 +6,12 @@ var prop = null
 
 func check_arg(arg = null) -> void:
 	if arg != null:
+		@warning_ignore("unsafe_call_argument")
 		print(check(arg))
 
 func check_recur() -> void:
 	if recur != null:
+		@warning_ignore("unsafe_call_argument")
 		print(check(recur))
 	else:
 		recur = 1
@@ -22,11 +24,13 @@ func test() -> void:
 
 	if prop == null:
 		set('prop', 1)
+		@warning_ignore("unsafe_call_argument")
 		print(check(prop))
 		set('prop', null)
 
 	var loop = null
 	while loop != 2:
 		if loop != null:
+			@warning_ignore("unsafe_call_argument")
 			print(check(loop))
 		loop = 1 if loop == null else 2