[TYPO3-english] Extbase/Fuild/Typo3 4.7.4 extension: RTE transformation decoding, how to do?

[Axel]

Hello,

I have a Extbase/Fluid/Typo3 4.7.4 content element extension with ts_css 
transformation:

[PHP]$TCA['tt_content']['types']['myext']['showitem'] = ..., 
myext_contact;Kontaktdaten;9;richtext[]:rte_transform[flag=rte_enabled|mode=ts_css];, 
...[/PHP]

I can't get the decoding right, so it shows this in the FE:

[HTML]...<br /> Tel.: +49 89 234234<br /> E-Mail: <link 
example at example.com - mail>Mail senden</link>... [/HTML]

I have tried to decode this in the extension with

[PHP]$this->view->assign('contact', 
$this->pi_RTEcssText($data['tx_myext_contact']));[/PHP]

or

[PHP]$this->view->assign('contact', 
tslib_pibase::pi_RTEcssText($data['tx_myext_contact']));[/PHP]

but this fails with the error message: " apache2: PHP Fatal error: Call 
to a member function parseFunc() on a non-object /pfad".

Does anyone know how to fix this or how to do this right in extbase/fluid?

Thanks a lot for any advice!

Best regards,

Axel