GDScript: Check if scripting has been disabled in VM

If scripting has been disabled, GDScript should stop processing
operations. The easiest way to do that is to check the scripting status
at the beginning of each loop in the VM.

modules/gdscript/gdscript_vm.cpp

@@ -686,6 +686,12 @@ Variant GDScriptFunction::call(GDScriptInstance *p_instance, const Variant **p_a
 #else
 	OPCODE_WHILE(true) {
 #endif
+		if (!ScriptServer::is_scripting_enabled()) {
+#ifdef DEBUG_ENABLED
+			exit_ok = true;
+#endif
+			OPCODE_BREAK;
+		}
 
 		OPCODE_SWITCH(_code_ptr[ip]) {
 			OPCODE(OPCODE_OPERATOR) {