Fix Segmentation fault: OnUpdateString->OnUpdateStringUnempty .

Author: cdoco

README.md

@@ -12,9 +12,7 @@
 
 ```shell
 $ git clone https://github.com/cdoco/hashids.phpc.git
-$ phpize
-$ ./configure
-$ make && make install
+$ cd hashids.phpc && phpize && ./configure && make && make install
 ```
 
 you can set some options in php.ini, or set in the constructor.

hashids.c

@@ -39,9 +39,9 @@ ZEND_BEGIN_ARG_INFO_EX(arginfo__construct, 0, 0, 3)
 ZEND_END_ARG_INFO()
 
 PHP_INI_BEGIN()
-    STD_PHP_INI_ENTRY("hashids.salt", HASHIDS_DEFAULT_SALT, PHP_INI_ALL, OnUpdateString, salt, zend_hashids_globals, hashids_globals)
+    STD_PHP_INI_ENTRY("hashids.salt", HASHIDS_DEFAULT_SALT, PHP_INI_ALL, OnUpdateStringUnempty, salt, zend_hashids_globals, hashids_globals)
     STD_PHP_INI_ENTRY("hashids.min_hash_length", "0", PHP_INI_ALL, OnUpdateLong, min_hash_length, zend_hashids_globals, hashids_globals)
-    STD_PHP_INI_ENTRY("hashids.alphabet", HASHIDS_DEFAULT_ALPHABET, PHP_INI_ALL, OnUpdateString, alphabet, zend_hashids_globals, hashids_globals)
+    STD_PHP_INI_ENTRY("hashids.alphabet", HASHIDS_DEFAULT_ALPHABET, PHP_INI_ALL, OnUpdateStringUnempty, alphabet, zend_hashids_globals, hashids_globals)
 PHP_INI_END()
 
 /* branch prediction hinting */