Section 46 says nothing of the sort. What it actually says is that the distribution of dividends must be authorised by board resolution (assuming that there is no legal obligation to distribute the dividend, in which case a board resolution isn't needed at all).
Authorising a resolution is not synonymous with signing it. Per section 73(8) of the Companies Act:
"Any minutes of a meeting, or a resolution, signed by the chair of the meeting, or by the chair of the next meeting of the board, is evidence of the proceedings of that meeting, or adoption of that resolution, as the case may be."
So the non-executive director can simply abstain from voting on financial decisions and not worry about having to sign anything.
If he wants to avoid any possibility of liability, then, per section 46(6), he must not be present at the meeting when the resolution is put to the board (which is fine since, per section 73(5b), only a majority of directors must be present at board meetings before a vote may be called - unanimous attendance is not required).
To the best of my knowledge, there is no way a director can be present at a meeting when a dividend resolution is put to vote and NOT be liable if they know that the distribution is contrary to the requirements of the Companies Act and fail to vote against it.
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