TinyMCE Wiris creating image instead of formula text and tries to upload it to server on content load

Question

I initialize TinyMCE:

        tinymce.init({
            selector: '#tiny_mce',
            images_upload_url: images_upload_url,
            external_plugins: {
                'tiny_mce_wiris': `@wiris/mathtype-tinymce6/plugin.min.js`,
            },

I have TinyMCE element with Wiris generated content in value:

<input id="tiny_mce" value="<math xmlns=&quot;http://www.w3.org/1998/Math/MathML&quot;><msqrt><mi>g</mi></msqrt>"/>
</math>

After TinyMCE is initiated and content above is loaded, TinyMCE generates image of Wiris math element and after that try to upload this image to server:

<img align="middle" class="Wirisformula" src="blob:http://localhost/050aec8d-0ae7-4112-905b-8be5aa8ee8b1" data-mathml="«math xmlns=¨http://www.w3.org/1998/Math/MathML¨»«msqrt»«mi»g«/mi»«/msqrt»«/math»" width="27" height="23" alt="square root of g" role="math" style="max-width: none; vertical-align: -4px;">

Server does not accept that image and getting message "Failed to upload image:...".

How to make TinyMCE to generate not image but text slectable contnet of Wiris formula?