That would be a brave bet imo, but you never know. You will be fine as long as the score is 0-0, but once a goal has been scored for either side, a second/third/fourth will come - depending on at what time the 1-0/0-1 was scored. If it's not 0-0 anymore, you will always have one of the teams needing to push and this normally leads to goals.
It could very well be, that it's 0-0 deep into HT2, because there is so much at stake and both teams don't want to take any risks, but I wouldn't feel comfortable with under 1.5 bet even in 80th minute with 0-0.
Since reintroduction of relegation playoffs in 2009, there were always 2+ goals in both legs combined. But there is a first for everything of course.
You have a good point here and I decided to change my bet. I will play first half without goals for medium stake and final result 0:0 for beer money. I quite like first half draw market for games with high rewards were teams play very cautiously and this time I feel comfortable enough to go for that goalless draw bet if odds are high enough.
Of course if the bookies give way too low odds I may skip the bet or go in a whole different direction. It is all about value odds in the end, at least for me