Can't install new Plugin

Hi,
i tried to install neu Plugin (cliffparnitzky/form-dependent-mandatory-field), but two days I have the same error:

Code:

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12:24:29 ERROR    [console] Error thrown while running command "cache:warmup --env=prod --no-ansi". Message: "Call to a member function isXmlHttpRequest() on null" ["exception" => Error { …},"command" => "cache:warmup --env=prod --no-ansi","message" => "Call to a member function isXmlHttpRequest() on null"]
In BaseWidget.php line 59:
                                                       
  Call to a member function isXmlHttpRequest() on null

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I use last Contao 4.10.3.
Anyone had a similar problem?