Work around images with size 0 in info

fixes #875

resources/qml/delegates/ImageMessage.qml

@@ -48,8 +48,8 @@ Item {
         smooth: true
         mipmap: true
 
-        sourceSize.width: Math.min(Screen.desktopAvailableWidth, originalWidth || undefined) * Screen.devicePixelRatio
-        sourceSize.height: Math.min(Screen.desktopAvailableHeight, originalWidth*proportionalHeight || undefined) * Screen.devicePixelRatio
+        sourceSize.width: Math.min(Screen.desktopAvailableWidth, originalWidth < 1 ? Screen.desktopAvailableWidth : originalWidth) * Screen.devicePixelRatio
+        sourceSize.height: Math.min(Screen.desktopAvailableHeight, (originalWidth < 1 ? Screen.desktopAvailableHeight : originalWidth*proportionalHeight)) * Screen.devicePixelRatio
     }
 
     MxcAnimatedImage {

src/MxcImageProvider.cpp

@@ -30,6 +30,9 @@ MxcImageProvider::requestImageResponse(const QString &id, const QSize &requested
     double radius = 0;
     auto size     = requestedSize;
 
+    if (requestedSize.width() == 0 && requestedSize.height() == 0)
+        size = QSize();
+
     auto queryStart = id.lastIndexOf('?');
     if (queryStart != -1) {
         id_            = id.left(queryStart);