p-button-link not visible in Material Design themes

[blurbiness]

In Material Design themes, the CSS for .p-button-link is:

.p-button.p-button-link {
  color: transparent;
  background: transparent;
  border: transparent;
}

All is transparent, so the button is completely hidden.
You can reproduce the behaviour in the showcase page:
https://primefaces.org/primevue/showcase/#/button

Pay attention to the basic link button. If you select a material design theme, it will dissapear.

[cagataycivici]

Thanks.