Replace a few #if/#elif with #ifdef and "#elif defined"

modules/gdnative/pluginscript/pluginscript_script.cpp

@@ -34,7 +34,7 @@
 #include "pluginscript_instance.h"
 #include "pluginscript_script.h"
 
-#if DEBUG_ENABLED
+#ifdef DEBUG_ENABLED
 #define __ASSERT_SCRIPT_REASON "Cannot retrieve pluginscript class for this script, is you code correct ?"
 #define ASSERT_SCRIPT_VALID()                \
 	{                                        \