Scrollbar does not descend to the end

I have a side menu that has a fixed position , if the screen resolution decreases, the scroll bar does not scroll down to the end, like this:

Currently I make this bar using the overflow property of css :

overflow: auto;

But all of the examples I saw in the position are set to absolute and not fixed .

How can I make this scroll bar go down to the end?

This is the% complete% of the menu:

#sidebar-wrapper {
  z-index: 1000;
  position: fixed;
  left: 230px;
  width: 0;
  height: 100%;
  margin-left: -230px;
  overflow-y: auto;
  background: #263238;
  -webkit-transition: all 0.5s ease;
  -moz-transition: all 0.5s ease;
  -o-transition: all 0.5s ease;
  transition: all 0.5s ease;
}