Fix the y-axis start point to 0 for impulse graphs
Fix the y-axis start point to 0 for impulse graphs

Avoids raising gnuplot error: "Warning empty y range [1:1]"

andreicristianpetcu/alaveteli,andreicristianpetcu/alaveteli_old,andreicristianpetcu/alaveteli,andreicristianpetcu/alaveteli,andreicristianpetcu/alaveteli,andreicristianpetcu/alaveteli_old,andreicristianpetcu/alaveteli_old,andreicristianpetcu/alaveteli_old,andreicristianpetcu/alaveteli_old,andreicristianpetcu/alaveteli