rewrite pppr_is_local

pppr_cookie.php

@@ -162,6 +162,14 @@ function get_PPPR_data() {
 }
 
 function pppr_is_local() {
-    $first_char =  $_COOKIE['PPPR'][0];
-    return $first_char === '1';
+    // Check if the cookie exists and is not empty
+    if (isset($_COOKIE['PPPR']) && !empty($_COOKIE['PPPR'])) {
+        // Ensure it's treated as a string before accessing the first character
+        $cookie_value = (string) $_COOKIE['PPPR'];
+        $first_char = $cookie_value[0] ?? '';
+        return $first_char === '1';
+    }
+    
+    // Return false if cookie is missing or empty
+    return false;
 }