Firefox 66 CSD css remove blank space

Question

Wanted to move close,min,max buttons to left in firefox 66 Ubuntu. Found the code below that did the job.

`@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul");


#TabsToolbar .toolbar-items {
    -moz-box-ordinal-group: 2;
}

#TabsToolbar-customization-target .titlebar-spacer[type="pre-tabs"] {
    display: none;
}

#TabsToolbar-customization-target .titlebar-spacer[type="post-tabs"] {
    width: 4px !important;
}

.titlebar-buttonbox-container {
    -moz-box-ordinal-group: 1 !important;
}

.titlebar-buttonbox-container toolbarbutton.titlebar-button.titlebar-close {
    margin-left: 4px !important;
}

However it creates a weird empty space block before the toggle buttons.

How can I modify the css code to remove that empty space?