Another variation of overflow in Conditional sections

Which happen after the previous fix to
https://bugzilla.gnome.org/show_bug.cgi?id=756456

But stopping the parser and exiting we didn't pop the intermediary entities
and doing the SKIP there applies on an input which may be too small

parser.c

@@ -6915,6 +6915,8 @@ xmlParseConditionalSections(xmlParserCtxtPtr ctxt) {
 	"All markup of the conditional section is not in the same entity\n",
 				 NULL, NULL);
 	}
+	if ((ctxt-> instate != XML_PARSER_EOF) &&
+	    ((ctxt->input->cur + 3) < ctxt->input->end))
 	    SKIP(3);
     }
 }