functions.inc.php: escape minus in regex

This makes CGP work on PHP 7.3 as it otherwise only shows an "Unknown
host" error message and logs the following PHP warning:

PHP Warning:  preg_match(): Compilation failed: invalid range in
character class at offset 4 in .../inc/functions.inc.php on line 37

1 files changed, 1 insertions, 1 deletions

diff --git a/inc/functions.inc.php b/inc/functions.inc.php
index 77cbe4b..376b6e1 100644
--- a/inc/functions.inc.php
+++ b/inc/functions.inc.php
@@ -34,7 +34,7 @@ function GET($index = NULL, $value = NULL) {
                 case 'h': # host
                 case 'pi': # plugin instance
                 case 'ti': # type instance
-                        if (!preg_match('/^[\w-.: ]+$/u', $value)) {
+                        if (!preg_match('/^[\w\-.: ]+$/u', $value)) {
                                 error_log(sprintf('Invalid %s in $_GET["%s"]: "%s"', $desc[$index], $index, $value));
                                 return NULL;
                         }