[libxml2] Fix debug dump of streaming XPath expressions

[Nick Wellnhofer <nwellnhof src gnome org>]

commit ca8635bfc23d67f6a9cce33733981ee768945b69
Author: Nick Wellnhofer <wellnhofer aevum de>
Date:   Thu Sep 7 15:46:12 2017 +0200

    Fix debug dump of streaming XPath expressions
    
    The debug function xmlXPathDebugDumpCompExpr would crash when
    called with a "streaming" expression.
    
    Fixes bug 787368.

 xpath.c |   15 +++++++++++----
 1 files changed, 11 insertions(+), 4 deletions(-)
---
diff --git a/xpath.c b/xpath.c
index 5b58c8f..2c1b268 100644
--- a/xpath.c
+++ b/xpath.c
@@ -1678,10 +1678,17 @@ xmlXPathDebugDumpCompExpr(FILE *output, xmlXPathCompExprPtr comp,
 
     fprintf(output, "%s", shift);
 
-    fprintf(output, "Compiled Expression : %d elements\n",
-           comp->nbStep);
-    i = comp->last;
-    xmlXPathDebugDumpStepOp(output, comp, &comp->steps[i], depth + 1);
+#ifdef XPATH_STREAMING
+    if (comp->stream) {
+        fprintf(output, "Streaming Expression\n");
+    } else
+#endif
+    {
+        fprintf(output, "Compiled Expression : %d elements\n",
+                comp->nbStep);
+        i = comp->last;
+        xmlXPathDebugDumpStepOp(output, comp, &comp->steps[i], depth + 1);
+    }
 }
 
 #ifdef XP_DEBUG_OBJ_USAGE