Fix use after free revealed by phpdbg

Author: weltling

ext/pcre/php_pcre.c

@@ -70,7 +70,7 @@ ZEND_TLS pcre_jit_stack *jit_stack = NULL;
 #if defined(ZTS) && defined(HAVE_PCRE_JIT_SUPPORT)
 static MUTEX_T pcre_mt = NULL;
 #define php_pcre_mutex_alloc() if (!pcre_mt) pcre_mt = tsrm_mutex_alloc();
-#define php_pcre_mutex_free() if (pcre_mt) tsrm_mutex_free(pcre_mt);
+#define php_pcre_mutex_free() if (pcre_mt) tsrm_mutex_free(pcre_mt); pcre_mt = NULL;
 #define php_pcre_mutex_lock() tsrm_mutex_lock(pcre_mt);
 #define php_pcre_mutex_unlock() tsrm_mutex_unlock(pcre_mt);
 #else