I already answered that question. My answer is that the question is moot, because the Scottish government is not so stupid nor so lacking in basic pragmatic reasoning as to seek to secede without the full cooperation and assent of the UK government. The UK government in 2016 is fundamentally reasonable, and will - perhaps with certain reasonable preconditions - readily assent to a further referendum and possible consequent independence if they are confident there is sufficient call for it in Scotland.
As I've said a few times now, I doubt the UK Government will assent to a referendum in advance of Brexit negotiations concluding, for the very good and sensible reason that since the EU situation is obviously the game-changer since the 2014 referendum, it only makes sense to wait for the reaction to the UK's new position in Europe before making any moves. The Scottish government would be crazy to reject or even resist such a condition, and they will not (IMO) reject or resist it.
So outside the "whys and wherefores", there is, in practice, zero chance that a confrontational, adversarial situation will ever arise where both UK and Scottish governments dig their heels in and raise the stakes to UDI levels. It's simply not in either side's best interests, and it's also entirely at odds with events to date: the 2014 referendum evolved from a negotiation resulting in the UK government granting assent for the referendum, and the current noises from Holyrood indicate that the same sort of negotiation is the way forward for a future referendum. I realise fully that some people appear to entertain a real appetite for conflict here, to the extent that they relish the thought of the "evil" English UK government disgustingly denying the brave Scottish people their God-given right to self-determination, and the mighty Scots seizing the day and proudly declaring independence against the will of the Evil Empire. But that's all strange and never-going-to-happen fantasy.
By all means, continue to pose needlessly provocative conundrums if you so desire. But nothing like that will ever happen. One might as well ask a question such as: if the UK parliament went loopy and voted to take the UK into war against France, what action would the UN take against the UK (Would it send bombers in to the UK? Would it order an invasion of the UK?)? It ain't going to happen. And similarly, the Scottish and UK parliaments failing to conduct a reasonable negotiation on a further referendum/independence, to the point where the Scottish government defies the UK government and holds a referendum anyhow (let alone declares independence without UK govt assent), simply ain't going to happen either. Ever.