Dragging a shader button into a button group crashes SM

[bencbartlett]

Reproduce:

1. Create new show
2. Create new button group
3. Create new shader button from library outside of the group (it seems as well that you can't add a button initially inside the group)
4. Drag button into group
5. SparkleMotion crashes

Something went horribly wrong.
No layout for test.
Stack Trace

    at GridLayout_0 (webpack-internal:///./kotlin-dce-dev/sparklemotion.js:128328:5)
    at div
    at eval (webpack-internal:///../../node_modules/@emotion/react/dist/emotion-element-cbed451f.browser.esm.js:57:66)
    at Paper (webpack-internal:///../../node_modules/@mui/material/Paper/Paper.js:88:82)
    at eval (webpack-internal:///../../node_modules/@emotion/react/dist/emotion-element-cbed451f.browser.esm.js:57:66)
    at Card (webpack-internal:///../../node_modules/@mui/material/Card/Card.js:53:82)
    at eval (webpack-internal:///./kotlin-dce-dev/kotlin-react-legacy.js:67:14)
    at eval (webpack-internal:///./kotlin-dce-dev/kotlin-react-legacy.js:67:14)
    at div
    at Resizable (webpack-internal:///../../node_modules/react-resizable/build/Resizable.js:46:35)
    at DraggableCore (webpack-internal:///../../node_modules/react-draggable/build/cjs/DraggableCore.js:134:5)
    at GridItem_0 (webpack-internal:///./kotlin-dce-dev/sparklemotion.js:127836:5)
    at div
    at GridLayout_0 (webpack-internal:///./kotlin-dce-dev/sparklemotion.js:128328:5)
    at div
    at eval (webpack-internal:///./kotlin-dce-dev/kotlin-react-legacy.js:67:14)
    at div
    at eval (webpack-internal:///./kotlin-dce-dev/kotlin-react-legacy.js:67:14)
    at eval (webpack-internal:///./kotlin-dce-dev/kotlin-react-legacy.js:67:14)
    at eval (webpack-internal:///./kotlin-dce-dev/kotlin-react-legacy.js:67:14)
    at ErrorBoundary (webpack-internal:///../../node_modules/react-error-boundary/dist/react-error-boundary.umd.js:45:37)
    at div
    at div
    at eval (webpack-internal:///../../node_modules/@emotion/react/dist/emotion-element-cbed451f.browser.esm.js:57:66)
    at Paper (webpack-internal:///../../node_modules/@mui/material/Paper/Paper.js:88:82)
    at InnerThemeProvider (webpack-internal:///../../node_modules/@mui/system/esm/ThemeProvider/ThemeProvider.js:23:70)
    at ThemeProvider (webpack-internal:///../../node_modules/@mui/private-theming/ThemeProvider/ThemeProvider.js:49:5)
    at ThemeProvider (webpack-internal:///../../node_modules/@mui/system/esm/ThemeProvider/ThemeProvider.js:43:5)
    at eval (webpack-internal:///./kotlin-dce-dev/kotlin-react-legacy.js:67:14)
    at ErrorBoundary (webpack-internal:///../../node_modules/react-error-boundary/dist/react-error-boundary.umd.js:45:37)
    at eval (webpack-internal:///./kotlin-dce-dev/kotlin-react-legacy.js:67:14)
    at div
    at div
    at div
    at InternalMosaicWindow (webpack-internal:///../../node_modules/react-mosaic-component/lib/MosaicWindow.js:51:47)
    at DragDropContainer (webpack-internal:///../../node_modules/react-dnd/dist/esm/decorators/decorateHandler.js:72:7)
    at DragDropContainer (webpack-internal:///../../node_modules/react-dnd/dist/esm/decorators/decorateHandler.js:72:7)
    at MosaicWindow (webpack-internal:///../../node_modules/react-mosaic-component/lib/MosaicWindow.js:239:42)
    at div
    at div
    at MosaicRoot (webpack-internal:///../../node_modules/react-mosaic-component/lib/MosaicRoot.js:40:47)
    at div
    at MosaicWithoutDragDropContext (webpack-internal:///../../node_modules/react-mosaic-component/lib/Mosaic.js:54:28)
    at eval (webpack-internal:///../../node_modules/react-dnd/dist/esm/common/DndProvider.js:29:23)
    at Mosaic (webpack-internal:///../../node_modules/react-mosaic-component/lib/Mosaic.js:165:42)
    at div
    at eval (webpack-internal:///./kotlin-dce-dev/kotlin-react-legacy.js:67:14)