preview pane split to two parts, can not see whole preview pics.

When I opened the preview pane, it had been split to two pars shown above, how can I get rid of the one below?
Confirmed on Atom 1.9.8 on Windows with graphviz-preview 1.7.0. I can temporarily get full height by adding height: 100% to the webview element, but since it is reconstructed with each save, this is not a great solution.
How to “adding height: 100% to the webview element”?
I am using windows7, and I have three version of Atom, 1.8.0 have no problem, 1.9.7 and 1.9.8 have the problem described above.
I'm on OS X 10.11.6, and have this problem in Atom 1.9.8 too. Earlier versions of Atom (can't remember which) didn't have the issue.
One can patch this locally by adding this to one's local stylesheet:
.graphviz-preview > webview {
height: 100%;
}
Confirmed on Ubuntu 16.04 running i3 as well.
Confirmed on Mac OS X 10.11.6 as well.
confirmed the issue even on Fedora 24 with atom 1.11.2
@GabVenturato if you need to edit/ preview graphviz, try the graphviz-preview-plus atom package if you haven't already.
I wrote that as an alternative to graphviz-preview - which doesn't seem to be maintained anymore.
@sverweij - thank you very much for hint - works like a charm!
@sverweij thank you very much, it seems excellent!
Change $HOME/.atom/packages/graphviz-preview/styles/graphviz-preview.less to
iframe, webview {
width: 100%;
height: 100%;
border: 0;
}
@perilbrain - thank your for dropping that hint!