Fix mistaken reverse logic in previous commit: would write "(null)" instead

of default style elements.

src/xpdev/ini_file.c

@@ -544,11 +544,11 @@ static char* ini_set_string(str_list_t* list, const char* section, const char* k
 
 	if(key==NULL)
 		return(NULL);
-	if(style->key_prefix==NULL)
+	if(style->key_prefix != NULL)
 		key_prefix = style->key_prefix;
-	if(style->value_separator==NULL)
+	if(style->value_separator != NULL)
 		value_separator = style->value_separator;
-	if(style->literal_separator==NULL)
+	if(style->literal_separator != NULL)
 		literal_separator = style->literal_separator;
 	if(value==NULL)
 		value="";