[PATCH] Don't copy sexpr node value that is an empty string

[Jim Fehlig <jfehlig@xxxxxxxx>]

Xen4.1 initializes some unspecified sexpr config items to an empty
string, unlike previous Xen versions that would leave the item unset.
E.g. the kernel item for an HVM guest (non-direct kernel boot):

Xen4.0 and earlier
  ...
  (image
    (hvm
      (kernel )
  ...

Xen4.1
  ...
  (image
    (hvm
      (kernel '')
  ...

The empty string for kernel causes some grief in subsequent parsing
where existence of specified kernel is checked, e.g.

  if (!def->os.kernel)
  ...

This patch solves the problem in sexpr_node_copy() by not copying
a node containing an empty string.
---
 src/util/sexpr.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/src/util/sexpr.c b/src/util/sexpr.c
index 0e30087..3523d76 100644
--- a/src/util/sexpr.c
+++ b/src/util/sexpr.c
@@ -519,7 +519,7 @@ int sexpr_node_copy(const struct sexpr *sexpr, const char *node, char **dst)
 {
     const char *val = sexpr_node(sexpr, node);
 
-    if (val) {
+    if (val && *val) {
         *dst = strdup(val);
         if (!(*dst))
             return -1;
-- 
1.7.7

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