Fix compilation issue while xml is disabled

src/request_body_processor/xml.h

@@ -13,9 +13,10 @@
  *
  */
 
-
+#ifdef WITH_LIBXML2
 #include <libxml/xmlschemas.h>
 #include <libxml/xpath.h>
+#endif
 
 #include <string>
 #include <iostream>
@@ -30,6 +31,7 @@
 namespace modsecurity {
 namespace RequestBodyProcessor {
 
+#ifdef WITH_LIBXML2
 
 struct xml_data {
     xmlSAXHandler *sax_handler;
@@ -63,6 +65,8 @@ class XML {
     std::string m_header;
 };
 
+#endif
+
 }  // namespace RequestBodyProcessor
 }  // namespace modsecurity