[HttpClient] Fix empty hosts in option "resolve"

Author: nicolas-grekas

HttpClientTrait.php

@@ -198,9 +198,8 @@ private static function mergeDefaultOptions(array $options, array $defaultOption
             $options['resolve'] = [];
             foreach ($resolve as $k => $v) {
                 if ('' === $v = (string) $v) {
-                    throw new InvalidArgumentException(sprintf('Option "resolve" for host "%s" cannot be empty.', $k));
-                }
-                if ('[' === $v[0] && ']' === substr($v, -1) && str_contains($v, ':')) {
+                    $v = null;
+                } elseif ('[' === $v[0] && ']' === substr($v, -1) && str_contains($v, ':')) {
                     $v = substr($v, 1, -1);
                 }
 
@@ -228,9 +227,8 @@ private static function mergeDefaultOptions(array $options, array $defaultOption
         if ($resolve = $defaultOptions['resolve'] ?? false) {
             foreach ($resolve as $k => $v) {
                 if ('' === $v = (string) $v) {
-                    throw new InvalidArgumentException(sprintf('Option "resolve" for host "%s" cannot be empty.', $k));
-                }
-                if ('[' === $v[0] && ']' === substr($v, -1) && str_contains($v, ':')) {
+                    $v = null;
+                } elseif ('[' === $v[0] && ']' === substr($v, -1) && str_contains($v, ':')) {
                     $v = substr($v, 1, -1);
                 }