Roll libxml to 2.9.3

third_party/libxml/src/error.c

 /*
  * error.c: module displaying/handling XML parser errors
  *
  * See Copyright for the status of this software.
  *
  * Daniel Veillard <daniel@veillard.com>
  */
 
 #define IN_LIBXML
 #include "libxml.h"
@@ skipping 159 matching lines @@
  */
 
 static void
 xmlParserPrintFileContextInternal(xmlParserInputPtr input ,
                 xmlGenericErrorFunc channel, void *data ) {
     const xmlChar *cur, *base;
     unsigned int n, col;        /* GCC warns if signed, because compared with sizeof() */
     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 */
     while ((cur > base) && ((*(cur) == '\n') || (*(cur) == '\r'))) {
         cur--;
     }
     n = 0;
     /* search backwards for beginning-of-line (to max buff size) */
     while ((n++ < (sizeof(content)-1)) && (cur > base) &&
            (*(cur) != '\n') && (*(cur) != '\r'))
@@ skipping 796 matching lines @@
     to->file = file;
     to->str1 = str1;
     to->str2 = str2;
     to->str3 = str3;
 
     return 0;
 }
 
 #define bottom_error
 #include "elfgcchack.h"