At the start of X-Men: Days of Future Past, it was explained that Trask was assassinated by Mystique in 1973 and the whole movie was basically about Wolverine going back in time to prevent that assassination. The mutants at the beginning of the film seem to be in continuity with the ones from X-Men: The Last Stand, so I'm assuming this part of X-Men: Days of Future Past is in the same timeline as X-Men: The Last Stand.
But then Trask does appear at the beginning of X-Men: The Last Stand as Secretary Trask, therefore the assassination could not have taken place in the first place. Is this a big gaping plot hole or did I read the continuity wrongly?
**Note: I'm aware that Trask was played by different actors in both movies. My question is on the continuity of Trask as a character in the movies. Given that the whole plot of X-Men: Days of Future Past revolves around preventing Trask's assassination, it would be a plot hole significant enough to invalidate the entire movie if the assassination never took place in the first place.