fix streaming scroll: use Timer.singleShot + positionViewAtIndex

gui/main.qml

@@ -313,14 +313,23 @@ ApplicationWindow {
                     boundsBehavior: Flickable.StopAtBounds
 
                     onCountChanged: {
-                        Qt.callLater(function() { positionViewAtEnd() })
+                        if (count > 0) {
+                            var idx = count - 1
+                            Timer.singleShot(0, function() {
+                                positionViewAtIndex(idx, ListView.End)
+                            })
+                        }
                     }
 
                     Connections {
                         target: chatModel
                         function onDataChanged() {
-                            if (chatView.atYEnd)
-                                Qt.callLater(function() { chatView.positionViewAtEnd() })
+                            if (chatView.atYEnd && chatView.count > 0) {
+                                var idx = chatView.count - 1
+                                Timer.singleShot(0, function() {
+                                    chatView.positionViewAtIndex(idx, ListView.End)
+                                })
+                            }
                         }
                     }