Fix crash in QPainter::drawGlyphRun() when painter is not active

Change-Id: I24f52cf1db300b8a6d0a4cb19fc6c74c41e00dbc
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@theqtcompany.com>

src/gui/painting/qpainter.cpp

@@ -5534,6 +5534,11 @@ void QPainter::drawGlyphRun(const QPointF &position, const QGlyphRun &glyphRun)
 {
     Q_D(QPainter);
 
+    if (!d->engine) {
+        qWarning("QPainter::drawGlyphRun: Painter not active");
+        return;
+    }
+
     QRawFont font = glyphRun.rawFont();
     if (!font.isValid())
         return;