php7.4 버전에서 경고메시지 나오는 문법 수정

lib/common.lib.php

@@ -3712,12 +3712,12 @@ function is_include_path_check($path='', $is_input='')
 
             try {
                 // whether $path is unix or not
-                $unipath = strlen($path)==0 || $path{0}!='/';
+                $unipath = strlen($path)==0 || substr($path, 0, 1) != '/';
                 $unc = substr($path,0,2)=='\\\\'?true:false;
                 // attempts to detect if path is relative in which case, add cwd
                 if(strpos($path,':') === false && $unipath && !$unc){
                     $path=getcwd().DIRECTORY_SEPARATOR.$path;
-                    if($path{0}=='/'){
+                    if(substr($path, 0, 1) == '/'){
                         $unipath = false;
                     }
                 }