Icons: warn about invalid resources

Also give a 1x1 pixmap back to avoid paint engine error messages.

Change-Id: Ibd7793d133952c4c3169796432b42572af0ace21
Reviewed-by: Alessandro Portale <alessandro.portale@qt.io>

src/libs/utils/icon.cpp

@@ -36,6 +36,7 @@
 #include <QPainter>
 #include <QPaintEngine>
 #include <QWidget>
+#include <QDebug>
 
 namespace Utils {
 
@@ -67,7 +68,12 @@ static MasksAndColors masksAndColors(const Icon &icon, int dpr)
         const QColor color = creatorTheme()->color(i.second);
         const QString dprFileName = StyleHelper::availableImageResolutions(i.first).contains(dpr) ?
                     StyleHelper::imageFileWithResolution(fileName, dpr) : fileName;
-        result.append(qMakePair(QPixmap(dprFileName), color));
+        QPixmap pixmap;
+        if (!pixmap.load(dprFileName)) {
+            pixmap = QPixmap(1, 1);
+            qWarning() << "Could not load image: " << dprFileName;
+        }
+        result.append({pixmap, color});
     }
     return result;
 }