Can't insert classic text

[swissspidy]

Tested using current master (d6b29f6) on Safari on macOS 10.13.

Steps to reproduce:

1. Click on Gutenberg -> New Post
2. Open inserter and select "Classic Text"

Expected: A new block is inserted

Actual result: The editor disappears.

JavaScript error in the console

[Error] React caught an error thrown by e. You should fix this error in your code. Consider adding an error boundary to your tree to customize error handling behavior.

Invariant Violation: Element type is invalid: expected a string (for built-in components) or a class/function (for composite components) but got: undefined. You likely forgot to export your component from the file it's defined in.

Check the render method of `e`.

The error is located at: 
    in e (created by e)
    in e (created by edit)
    in edit (created by t)
    in div (created by t)
    in div (created by t)
    in t (created by Connect(t))
    in Connect(t) (created by t)
    in div (created by t)
    in t (created by Connect(t))
    in Connect(t) (created by t)
    in div (created by t)
    in t (created by Connect(t))
    in Connect(t) (created by o)
    in div (created by o)
    in div (created by o)
    in o (created by Connect(o))
    in Connect(o)
    in t
    in Provider

The error was thrown at: 
    invariant@http://local.wordpress.dev/wp-content/plugins/gutenberg/vendor/react-dom.e5cfcfc9.js?ver=4.8:154:24,
    createFiberFromElementType@http://local.wordpress.dev/wp-content/plugins/gutenberg/vendor/react-dom.e5cfcfc9.js?ver=4.8:11619:16,
    createFiberFromElement@http://local.wordpress.dev/wp-content/plugins/gutenberg/vendor/react-dom.e5cfcfc9.js?ver=4.8:11564:41,
    reconcileSingleElement@http://local.wordpress.dev/wp-content/plugins/gutenberg/vendor/react-dom.e5cfcfc9.js?ver=4.8:12795:43,
    reconcileChildFibers@http://local.wordpress.dev/wp-content/plugins/gutenberg/vendor/react-dom.e5cfcfc9.js?ver=4.8:12905:59,
    reconcileChildrenAtPriority@http://local.wordpress.dev/wp-content/plugins/gutenberg/vendor/react-dom.e5cfcfc9.js?ver=4.8:13565:53,
    reconcileChildren@http://local.wordpress.dev/wp-content/plugins/gutenberg/vendor/react-dom.e5cfcfc9.js?ver=4.8:13553:32,
    finishClassComponent@http://local.wordpress.dev/wp-content/plugins/gutenberg/vendor/react-dom.e5cfcfc9.js?ver=4.8:13698:22,
    performUnitOfWork@http://local.wordpress.dev/wp-content/plugins/gutenberg/vendor/react-dom.e5cfcfc9.js?ver=4.8:15966:25,
    workLoop@http://local.wordpress.dev/wp-content/plugins/gutenberg/vendor/react-dom.e5cfcfc9.js?ver=4.8:16088:43,
    boundFunc@http://local.wordpress.dev/wp-content/plugins/gutenberg/vendor/react-dom.e5cfcfc9.js?ver=4.8:1462:19,
    dispatchEvent@[native code],
    invokeGuardedCallback@http://local.wordpress.dev/wp-content/plugins/gutenberg/vendor/react-dom.e5cfcfc9.js?ver=4.8:1476:29,
    performWork@http://local.wordpress.dev/wp-content/plugins/gutenberg/vendor/react-dom.e5cfcfc9.js?ver=4.8:16126:42,
    batchedUpdates@http://local.wordpress.dev/wp-content/plugins/gutenberg/vendor/react-dom.e5cfcfc9.js?ver=4.8:16572:20,
    batchedUpdatesWithControlledComponents@http://local.wordpress.dev/wp-content/plugins/gutenberg/vendor/react-dom.e5cfcfc9.js?ver=4.8:1828:26,
    dispatchEvent@http://local.wordpress.dev/wp-content/plugins/gutenberg/vendor/react-dom.e5cfcfc9.js?ver=4.8:2025:44,
    dispatchEvent@[native code]
	logCapturedError$1 (react-dom.e5cfcfc9.js:11744)
	commitErrorHandling (react-dom.e5cfcfc9.js:16381)
	commitAllLifeCycles (react-dom.e5cfcfc9.js:15699)
	boundFunc (react-dom.e5cfcfc9.js:1462)
	dispatchEvent
	invokeGuardedCallback (react-dom.e5cfcfc9.js:1476)
	commitAllWork (react-dom.e5cfcfc9.js:15798)
	completeUnitOfWork (react-dom.e5cfcfc9.js:15941)
	performWork (react-dom.e5cfcfc9.js:16156)
	batchedUpdates (react-dom.e5cfcfc9.js:16572)
	batchedUpdatesWithControlledComponents (react-dom.e5cfcfc9.js:1828)
	dispatchEvent (react-dom.e5cfcfc9.js:2025)
	dispatchEvent

---

What sticks out is this: You likely forgot to export your component from the file it's defined in.

So, which one is it?

[swissspidy]

OK, so this seems to happen with existing posts as well.