Launcher: fix preview image aspect ratio

Accidentally left in a hard-coded 16:9 ratio, no wonder some images got
squished. Shuttle is now re-elongated verticallitaly :)

src/GUI/PreviewImageItem.cxx

@@ -73,6 +73,11 @@ bool PreviewImageItem::isLoading() const
     return m_requestActive;
 }
 
+float PreviewImageItem::aspectRatio() const
+{
+    return static_cast<float>(m_image.width()) / m_image.height();
+}
+
 void PreviewImageItem::setImageUrl( QUrl url)
 {
     if (m_imageUrl == url)

src/GUI/PreviewImageItem.hxx

@@ -20,6 +20,7 @@ class PreviewImageItem : public QQuickItem
 
     Q_PROPERTY(bool isLoading READ isLoading NOTIFY isLoadingChanged)
 
+    Q_PROPERTY(float aspectRatio READ aspectRatio NOTIFY sourceSizeChanged)
 public:
     PreviewImageItem(QQuickItem* parent = nullptr);
     ~PreviewImageItem();
@@ -34,6 +35,8 @@ public:
 
     bool isLoading() const;
 
+    float aspectRatio() const;
+
 signals:
     void imageUrlChanged();
     void sourceSizeChanged();

src/GUI/qml/AircraftPreviewPanel.qml

@@ -11,7 +11,7 @@ Rectangle {
         activePreview = 0
     }
 
-    height: width / (16/9)
+    height: width / preview.aspectRatio
     color: "#7f7f7f"
 
     border.width: 1
@@ -22,6 +22,7 @@ Rectangle {
     }
 
     PreviewImage {
+        id: preview
         width: parent.width
         height: parent.height
         imageUrl: __havePreviews ? root.previews[root.activePreview] : ""