Near-zero bars cause problem in picking

In the picture below, some of the bars' heights are so close to 0 (like 0.09) (e.g: (the blue one with label)). These bars with a height of 0 cause the selection feature to be broken. When I want to select the bars behind it, it acts as if I chose this bar and blocks the others in a way.
 
The example that I'm talking about is qmllegend and it in the qtdatavis3d repo, under wip/NG. The SHA for that one is 457afc271c413b8af79fadc9e356f42b344eab2d. I also added a file which will make debugging easier when applied on top of the SHA.