Be careful: QColor::fromHslF can sometimes return an invalid qcolor

Which causes asserts.

QColor::fromHsvF: HSV parameters out of range
Could not construct valid color from h 0.833333 s 1 l -8.63674e-28 a 1

krita/ui/canvas/kis_display_color_converter.cpp

@@ -494,8 +494,7 @@ QImage KisDisplayColorConverter::toQImage(KisPaintDeviceSP srcDevice) const
     return QImage();
 }
 
-KoColor
-KisDisplayColorConverter::Private::approximateFromQColor(const QColor &qcolor)
+KoColor KisDisplayColorConverter::Private::approximateFromQColor(const QColor &qcolor)
 {
     if (!useOcio()) {
         return KoColor(qcolor, paintingColorSpace);
@@ -555,7 +554,12 @@ KoColor KisDisplayColorConverter::fromHslF(qreal h, qreal s, qreal l, qreal a)
 {
     // generate HSL from sRGB!
     QColor qcolor(QColor::fromHslF(h, s, l, a));
+    if (!qcolor.isValid()) {
+        qWarning() << "Could not construct valid color from h" << h << "s" << s << "l" << l << "a" << a;
+        qcolor = Qt::black;
+    }
     return m_d->approximateFromQColor(qcolor);
+
 }
 
 void KisDisplayColorConverter::getHslF(const KoColor &srcColor, qreal *h, qreal *s, qreal *l, qreal *a)