get error

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<b>Warning</b>:  Cannot modify header information - headers already sent by (output started at /data01/virt30108/domeenid/www.tehnopol.ee/livinglabsummit/index.php:4) in <b>/data01/virt30108/domeenid/www.tehnopol.ee/livinglabsummit/wp-includes/rest-api/class-wp-rest-server.php</b> on line <b>1648</b><br />
<br />
<b>Warning</b>:  Cannot modify header information - headers already sent by (output started at /data01/virt30108/domeenid/www.tehnopol.ee/livinglabsummit/index.php:4) in <b>/data01/virt30108/domeenid/www.tehnopol.ee/livinglabsummit/wp-includes/rest-api/class-wp-rest-server.php</b> on line <b>1648</b><br />
<br />
<b>Warning</b>:  Cannot modify header information - headers already sent by (output started at /data01/virt30108/domeenid/www.tehnopol.ee/livinglabsummit/index.php:4) in <b>/data01/virt30108/domeenid/www.tehnopol.ee/livinglabsummit/wp-includes/rest-api/class-wp-rest-server.php</b> on line <b>1648</b><br />
<br />
<b>Warning</b>:  Cannot modify header information - headers already sent by (output started at /data01/virt30108/domeenid/www.tehnopol.ee/livinglabsummit/index.php:4) in <b>/data01/virt30108/domeenid/www.tehnopol.ee/livinglabsummit/wp-includes/rest-api/class-wp-rest-server.php</b> on line <b>1648</b><br />
<br />
<b>Warning</b>:  Cannot modify header information - headers already sent by (output started at /data01/virt30108/domeenid/www.tehnopol.ee/livinglabsummit/index.php:4) in <b>/data01/virt30108/domeenid/www.tehnopol.ee/livinglabsummit/wp-includes/rest-api/class-wp-rest-server.php</b> on line <b>1648</b><br />
<br />
<b>Warning</b>:  Cannot modify header information - headers already sent by (output started at /data01/virt30108/domeenid/www.tehnopol.ee/livinglabsummit/index.php:4) in <b>/data01/virt30108/domeenid/www.tehnopol.ee/livinglabsummit/wp-includes/rest-api/class-wp-rest-server.php</b> on line <b>1648</b><br />
<br />
<b>Warning</b>:  Cannot modify header information - headers already sent by (output started at /data01/virt30108/domeenid/www.tehnopol.ee/livinglabsummit/index.php:4) in <b>/data01/virt30108/domeenid/www.tehnopol.ee/livinglabsummit/wp-includes/rest-api/class-wp-rest-server.php</b> on line <b>1648</b><br />
{"id":2,"name":"lls_haldur","url":"","description":"","link":"https:\/\/livinglabsummit.tehnopol.ee\/author\/lls_haldur\/","slug":"lls_haldur","avatar_urls":{"24":"https:\/\/secure.gravatar.com\/avatar\/9d0e4f5c2b22c012f8a07750b64776a8?s=24&d=mm&r=g","48":"https:\/\/secure.gravatar.com\/avatar\/9d0e4f5c2b22c012f8a07750b64776a8?s=48&d=mm&r=g","96":"https:\/\/secure.gravatar.com\/avatar\/9d0e4f5c2b22c012f8a07750b64776a8?s=96&d=mm&r=g"},"meta":[],"acf":[],"_links":{"self":[{"href":"https:\/\/livinglabsummit.tehnopol.ee\/wp-json\/wp\/v2\/users\/2"}],"collection":[{"href":"https:\/\/livinglabsummit.tehnopol.ee\/wp-json\/wp\/v2\/users"}]}}