Error: MUI: Unsupported var(--mui-palette-common-white) color.

[Hammad1029]

I just followed the example in the getting started section of the documentation. This is my code:

const rteRef = useRef<RichTextEditorRef>(null);

 <RichTextEditor
              ref={rteRef}
              extensions={[]}
              content="<p>Hello world</p>"
              renderControls={() => (
                <MenuControlsContainer>
                  <MenuSelectHeading />
                  <MenuDivider />
                  <MenuButtonBold />
                  <MenuButtonItalic />
                </MenuControlsContainer>
              )}
            />

But I keep getting this error:

Unhandled Runtime Error
Error: MUI: Unsupported `var(--mui-palette-common-white)` color.
The following formats are supported: #nnn, #nnnnnn, rgb(), rgba(), hsl(), hsla(), color().

Any clues as to why?