Red Background in QTreeWidget

Kangon

I was trying to change the icon of an item in my QTreeWidget, but the red background keeps appearing. It is always visible, whether I click on an item or not.
My stylesheet looks like this:

/* Grundlayout für das TreeWidget */
QListWidget {
background: #121418;
color: #e6e6e6;
border: 1px solid #2a2e36;
border-radius: 8px;
padding: 4px;
outline: none;
}

/* Hover-Effekt /
QListWidget::item:hover {
background: #8a9ba8; / helleres Orange beim Überfahren */
color: black;
outline: none;
}

QListWidget::item:selected {
background: #5c7080; /* helleres Orange beim Überfahren */
color: black;
outline: none;
}

/* Basis */
QScrollBar {
background: transparent;
margin: 0px;
}

/* Vertikal /
QScrollBar:vertical {
width: 8px;
}
QScrollBar::handle:vertical {
background: rgba(238, 125, 0, 0.3); / dezent orange /
min-height: 20px;
border-radius: 4px;
}
QScrollBar::handle:vertical:hover {
background: #ee7d00; / volle Farbe beim Hover */
}
QScrollBar::add-line:vertical,
QScrollBar::sub-line:vertical {
background: none;
height: 0px;
border: none;
}
QScrollBar::add-page:vertical,
QScrollBar::sub-page:vertical {
background: transparent;
}

/* Horizontal */
QScrollBar:horizontal {
height: 8px;
}
QScrollBar::handle:horizontal {
background: rgba(238, 125, 0, 0.3);
min-width: 20px;
border-radius: 4px;
}
QScrollBar::handle:horizontal:hover {
background: #ee7d00;
}
QScrollBar::add-line:horizontal,
QScrollBar::sub-line:horizontal {
background: none;
width: 0px;
border: none;
}
QScrollBar::add-page:horizontal,
QScrollBar::sub-page:horizontal {
background: transparent;
}