[libxml2] Do not print error context when there is none

[Daniel Veillard <veillard src gnome org>]

commit ce0b0d0d81fdbb5f722a890432b52d363e4de57b
Author: Daniel Veillard <veillard redhat com>
Date:   Fri Nov 20 15:01:22 2015 +0800

    Do not print error context when there is none
    
    Which now happens more frequently du to xmlHaltParser use

 error.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)
---
diff --git a/error.c b/error.c
index cbcf5c9..9c45040 100644
--- a/error.c
+++ b/error.c
@@ -177,7 +177,9 @@ xmlParserPrintFileContextInternal(xmlParserInputPtr input ,
     xmlChar  content[81]; /* space for 80 chars + line terminator */
     xmlChar *ctnt;
 
-    if (input == NULL) return;
+    if ((input == NULL) || (input->cur == NULL) ||
+        (*input->cur == 0)) return;
+
     cur = input->cur;
     base = input->base;
     /* skip backwards over any end-of-lines */