You should always put the end locks on the weight bars so that the weights will not fall off. You may not think you need them because you are lifting light weights, but a weight bar can become unbalanced no matter how little or how much weight you are lifting, and once the bar becomes unbalanced and you lose control anything could happen.
When I was in high school, we were lifting weights on the bench press and there were four of us, so we had two guys spotting all the time. One guy was on each end of the bar in case the person lifting needed help.
One guy was lifting and he started to struggle with the weights. One of the guys spotting grabbed his end of the bar and lifted. I was on the other end and I was waiting to see whether the guy would be able to lift the weights on his on. When the other spotter lifted on the bar, the weights on my side slid off and the bar became unbalanced.
The bar flew up and popped me right in the mouth. A few months later and several trips to the dentist and I was as good as new. Always use the weight bar collars.