cgi: Fix showing query string in Help

If a string was searched on CUPS Web UI help page, garbage was printed out in search box. It was because text field pointer was freed before and contained garbage - previously it was variable value which was allocated, so the string survived cgCleanVariables((), but the text field is a pointer into form variables which gets cleaned up.

Fix is to use strdup() if cgiGetTextfield() returns non-NULL pointer. The binary exits shortly after either way, so memory is taken care of by OS.

cgi-bin/help.c

@@ -28,7 +28,7 @@ main(int argc, /* I - Number of command-line arguments */
  *si; /* Search index */
  help_node_t *n; /* Current help node */
  int i; /* Looping var */
- const char *query;  /* Search query */
+ const char *query = NULL; /* Search query */
  const char *cache_dir; /* CUPS_CACHEDIR environment variable */
  const char *docroot; /* CUPS_DOCROOT environment variable */
  const char *helpfile, /* Current help file */
@@ -172,8 +172,9 @@ main(int argc, /* I - Number of command-line arguments */
 
  if (cgiGetVariable("CLEAR"))
  cgiSetVariable("QUERY", "");
+ else if ((query = cgiGetTextfield("QUERY")) != NULL)
+ query = strdup(query);
 
- query = cgiGetTextfield("QUERY");
  si = helpSearchIndex(hi, query, topic, helpfile);
 
  cgiClearVariables();