Cancel drag and drop if there is no screenshot in the preview.

src/Gui/KSWidget.cpp

@@ -174,6 +174,7 @@ KSWidget::KSWidget(Platform::GrabModes theGrabModes, QWidget *parent)
     mPlaceholderLabel->setTextInteractionFlags(Qt::NoTextInteraction);
     mPlaceholderLabel->setWordWrap(true);
     mPlaceholderLabel->setAlignment(Qt::AlignCenter);
+    mPlaceholderLabel->setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
     // Match opacity of QML placeholder label component
     auto *effect = new QGraphicsOpacityEffect(mPlaceholderLabel);
     effect->setOpacity(0.5);
@@ -227,6 +228,7 @@ bool KSWidget::isScreenshotSet()
 
 void KSWidget::showPlaceholderText(const QString &label)
 {
+    mImageWidget->hide();
     mPlaceholderLabel->setText(label);
     mPlaceholderLabel->show();
 }
@@ -236,6 +238,7 @@ void KSWidget::setScreenshotPixmap(const QPixmap &thePixmap)
     if (mPlaceholderLabel->isVisible()) {
         mPlaceholderLabel->hide();
     }
+    mImageWidget->show();
     mImageWidget->setScreenshot(thePixmap);
 }
 

src/SpectacleCore.cpp

@@ -518,6 +518,9 @@ void SpectacleCore::populateCommandLineParser(QCommandLineParser *lCmdLineParser
 void SpectacleCore::doStartDragAndDrop()
 {
     auto lExportManager = ExportManager::instance();
+    if (lExportManager->pixmap().isNull()) {
+        return;
+    }
     QUrl lTempFile = lExportManager->tempSave();
     if (!lTempFile.isValid()) {
         return;