Update mbstring.c

Author: wkhudgins92

ext/mbstring/mbstring.c

@@ -2642,7 +2642,7 @@ PHP_FUNCTION(mb_str_begins)
                 break;
             default:
 				char buffer[42];
-				sprintf(buffer, "Unknown error in mb_strpos. Error code: %d", n);
+				sprintf(buffer, "Unknown error in mb_strpos. Error code: %zu", n);
                 php_error_docref(NULL, E_WARNING, buffer);
                 break;
         }
@@ -2723,7 +2723,7 @@ PHP_FUNCTION(mb_str_ends)
                 break;
             default:
 				char buffer[42];
-				sprintf(buffer, "Unknown error in mb_strpos. Error code: %d", n);
+				sprintf(buffer, "Unknown error in mb_strpos. Error code: %zu", n);
                 php_error_docref(NULL, E_WARNING, buffer);
                 break;
         }