Sources for the dummy bombs please. And even if they have done something, it does not excuse them from blatantly attacking civilians when there is absolutely no military objective to be gained by doing so. It is in fact a war crime.
Any attack on civilians where there is no evidence of Hamas being anywhere near the bombing site is an intentional bombing act that only killed civilians. It is entirely irrelevant what Israel intended; they did not properly discharge their responsibility regarding not endangering civilians.
It does not excuse them from killing civilians, but it does disapprove that they had intention. Unfortunately, in any war there are civilian casualties. I mean in WWII, civilian casualties were twice that of military casualties. And since Hamas wear civilian clothes, it makes the job even more difficult for the Israelis to differentiate and target properly. So, for a war, Israel has done a lot of effort to warn the civilians. The Hamas asked for a war, so they got it.
I read about the dummy rockets in an article somewhere, but they also have it on wiki.