fix: guard blocknote popover references

src/lib/blockNotePopover.regression.test.ts

@@ -0,0 +1,15 @@
+import { describe, expect, it } from 'vitest'
+import { getMountedBoundingClientRectCache } from '@blocknote/react'
+
+describe('patched BlockNote popover references', () => {
+  it('uses the virtual rect when a remounting suggestion menu has no DOM element', () => {
+    const fallbackRect = new DOMRect(4, 8, 16, 24)
+    const readRect = getMountedBoundingClientRectCache({
+      element: undefined,
+      getBoundingClientRect: () => fallbackRect,
+    } as never)
+
+    expect(() => readRect()).not.toThrow()
+    expect(readRect()).toBe(fallbackRect)
+  })
+})