Unable to close pages in Firefox after hiding the tab bar

Question

In my style.css (which affects the look of Firefox) I hid the tab bar using

    display: none !important;

which should only hide the tab bar. But now when I go to close tabs (using "d" in vimperator) I get this error :

    TypeError: this.selectedItem is null

which looks to be some form of JS or jQuery. Does Firefox actually need that tab bar? My browser is practically unusable with the CSS turned on. If anyone knows how to fix it that be great

Here's the CSS that I believe is causing the problem

       /* TABS */
.tabbrowser-tab[fadein]:not([pinned]) { min-width: 100px !important; max-width: /*180px*/ 100% !important; }
tab {
    font-family: var(--tab-fonts) !important;
    height:1px !important; min-height: 1px !important;
    font-size: var(--tab-font-size); text-shadow: none !important; text-align: left /* center | left */ !important;
}

.tabbrowser-tab label { padding: 0 22px 0 22px !important; display: none !important;  }

#tabbrowser-tabs .tabbrowser-tab[pinned]            { width: 1px !important; }
#tabbrowser-tabs .tabbrowser-tab[pinned] label      { display: none !important; }

#tabbrowser-tabs .tabbrowser-tab .tab-icon-image {
    margin: 0 -10px 0 16px !important;
    width: var(--tab-icon-size) !important;
    height: 1px !important;
}

.tab-icon-image {
    display: none !important;
}

.tabbrowser-tab *, .tabs-newtab-button * {
    background: #7E9C7A!important; list-style-image: none !important;
    margin: 0 0 0 0 !important; padding: 0 0 0 0 !important;
    -moz-appearance: none !important;
}

#tabbrowser-tabs .tabbrowser-tab[pinned] .tab-stack { height: 1px !important; width: 100% !important; }
#tabbrowser-tabs .tabbrowser-arrowscrollbox .box-inherit.scrollbox-innerbox { max-height: 1px !important; }
.scrollbutton-up, .scrollbutton-down { border: none !important; }

#tabbrowser-tabs[overflow]:not([positionpinnedtabs]) { -moz-padding-start: 20px !important; }

.tabbrowser-tab[selected="true"] .tab-stack {
            background-color: #FFFFFF!important;
    border-radius: 0px !important; position: relative !important;
    /*border-top: 1px solid #dc52a5 !important;/**/
}
.tabbrowser-tab[selected="true"]:before { /* Left Triangle (of selected tab) */
    content: '' !important; display: var(--tab-triangle);
    position: absolute !important; top: 0 !important; left: var(--tab-overlap) !important;
    width: 0 !important; height: 0 !important;
    border: none !important; z-index: 2 !important;

    /*border-left: calc(var(--tab-height)/2) solid var(--bg-dark) !important;
    border-top: calc((var(--tab-height)/2) - var(--tab-triangle-correction)) solid var(--bg-light) !important;
    border-bottom: calc((var(--tab-height)/2) + var(--tab-triangle-correction)) solid var(--bg-light) !important;/**/
    /**/border-top: var(--tab-height) solid  #7E9C7A !important;
    border-right: calc(var(--tab-height)/2) solid  #7E9C7A !important;/**/
}
.tabbrowser-tab[selected="true"]:after { /* Right Triangle (of selected tab) */
    content: '' !important; display: var(--tab-triangle);
    position: absolute !important; top: 0 !important; right: var(--tab-overlap) !important;
    width: 0 !important; height: 0 !important;
    border: none !important; z-index: 0 !important;

    /*border-right: calc(var(--tab-height)/2) solid var(--bg-dark) !important;
    border-top: calc((var(--tab-height)/2) - var(--tab-triangle-correction)) solid var(--bg-light) !important;
    border-bottom: calc((var(--tab-height)/2) + var(--tab-triangle-correction)) solid var(--bg-light) !important;/**/
    /**/border-top: var(--tab-height) solid #7E9C7A !important;
    border-left: calc(var(--tab-height)/2) solid #7E9C7A !important;/**/
}



#TabsToolbar, #tabbrowser-tabs {
    -moz-appearance: none !important;
    height: 1px !important; width: 0px !important;
    margin: 0 var(--tab-strip-margin) !important;
    background-color: #7E9C7A!important;
    display: none !important;

    /* --- Uncomment the line below to attach the url-bar to the tab-bar [EXPERIMENTAL] (Require a line in "#nav-bar" above) --- */
    /*margin-left: 150px !important;/**/
}
#TabsToolbar::after { display: none !important; }
.tabbrowser-tab::before, .tabbrowser-tab::after { background: none !important; }