Describe the bug
When opening the menu for a block close to the bottom of the viewport the positioning is inconsistent.

To Reproduce

Reproduced in https://www.blocknotejs.org/examples/basic/minimal

Position content and editor so the empty block is close to the bottom of the viewport (but not too close)

Click on a plus once, the menu is positioned above the empty block:

Click on same plus second time, the menu is positioned below and very small:

Misc

• Node version: 22.2.0
• Package manager: yarn
• Browser: Firefox 129.0.2
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