it is pretty much like Celambarasan said, Qlikview will automatically align to the center so that the gaps will be there.
I've tried looking at your file. While it isn't particularly elegant, multiplying your line chart might give you the look of what you want. Basically it is two line charts on top of each other. The one that actually contains the chart is much larger an transparent, so it can see the scale of the second chart.
Maybe somebody has a more elegant solution that this?