fix: parse flag error on elem is empty string

Signed-off-by: inhere <[email protected]>

Author: inhere

Diff for: src/Flags.php

@@ -133,6 +133,11 @@ public static function parseArgv(array $params, array $config = []): array
         while (false !== ($p = current($params))) {
             next($params);
 
+            // empty string
+            if ($p === '') {
+                continue;
+            }
+
             // is options
             if ($p[0] === '-') {
                 $value  = true;