useRealm must be used within a RealmContextProvider

I'm trying to add a single h1 button instead of BlockTypeSelect, but I keep getting this error.

Here's my code
`export function WysiwygEditor() {
const ref = React.useRef(null);
const [value, setValue] = useState('');
const applyBlockType = usePublisher(applyBlockType$);

return (
    <MDXEditor
        ref={ref}
        iconComponentFor={(name) => WysiwygEditorIconByName[name]}
        plugins={[
            toolbarPlugin({
                toolbarContents: () => (
                    <>
                        <BoldItalicUnderlineToggles />
                        <StrikeThroughSupSubToggles
                            options={['Strikethrough']}
                        />
                        <BlockTypeSelect />
                        <Separator />
                        <Button
                            onClick={() => {
                                applyBlockType('h1');
                            }}
                        >
                            <TextHeading1Icon />
                        </Button>
                    </>
                ),
            }),
            headingsPlugin({ allowedHeadingLevels: [1, 2] }),
        ]}
        markdown={value}
        onChange={(markdown) => setValue(markdown)}
    />
);

}`

Start with the WysiwygEditor example and compare the custom applyBlockType button with BlockTypeSelect. Trace usePublisher(applyBlockType$) and RealmContextProvider usage in the editor entry points, then reproduce the reported error. Done means the supported custom heading-button usage is clarified or the reported failure is fixed and covered by an appropriate test.