not upstream yet, fix from nmehta@
see https://docs.google.com/document/d/1-Cd_Yq8MZ7am2ZhKhbDhqZ_L0aLJPBg0w1QLXGVoNmY/edit
and https://bugs.chromium.org/p/chromium/issues/detail?id=705445

--- src/xpath.c	2016-12-25 17:26:52.000000000 -0800
+++ src/xpath.c	2017-03-30 11:15:41.000000000 -0700
@@ -4368,7 +4368,7 @@
     }
     memset(ret, 0 , (size_t) sizeof(xmlXPathObject));
     ret->type = XPATH_XSLT_TREE;
-    ret->boolval = 1;
+    ret->boolval = 0;
     ret->user = (void *) val;
     ret->nodesetval = xmlXPathNodeSetCreate(val);
 #ifdef XP_DEBUG_OBJ_USAGE