Use dialogs from qt labs platform and fix a image downloading bug.

imports/Spectral/Component/Timeline/ImageDelegate.qml

@@ -27,8 +27,14 @@ ColumnLayout {
     spacing: 0
 
     onDownloadedChanged: {
-        if (downloaded && showOnFinished) showSavedFile()
-        if (downloaded && openOnFinished) openSavedFile()
+        if (downloaded && showOnFinished) {
+            showSavedFile()
+            showOnFinished = false
+        }
+        if (downloaded && openOnFinished) {
+            openSavedFile()
+            openOnFinished = false
+        }
     }
 
     Label {
@@ -183,9 +189,9 @@ ColumnLayout {
                 }
 
                 Component {
-                    id: openFileDialog
+                    id: openFolderDialog
 
-                    OpenFileDialog {}
+                    OpenFolderDialog {}
                 }
 
                 Component {
@@ -204,15 +210,15 @@ ColumnLayout {
     }
 
     function saveFileAs() {
-        var fileDialog = openFileDialog.createObject(ApplicationWindow.overlay, {"selectFolder": true})
+        var folderDialog = openFolderDialog.createObject(ApplicationWindow.overlay)
 
-        fileDialog.chosen.connect(function(path) {
+        folderDialog.chosen.connect(function(path) {
             if (!path) return
 
             currentRoom.downloadFile(eventId, path + "/" + (content.filename || content.body))
         })
 
-        fileDialog.open()
+        folderDialog.open()
     }
 
     function downloadAndShow()