Add workaround for delegate stuck transition bug

Sometimes and randomly, a HListView/HGridView delegate's
add/populate transition will stop before completion.

This especially happens on startup when loading a large room list,
one room might get stuck and left tiny or invisible, despite its
normal space still being taken.

src/gui/Base/DelegateTransitionFixer.qml

@@ -0,0 +1,35 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+
+import QtQuick 2.12
+
+Timer {
+    // Sometimes and randomly, a HListView/HGridView delegate's add/populate
+    // Transition will stop too early, leaving a stuck invisible or tiny item.
+    // This is a workaround for this Qt bug happening despite the neccessary
+    // Transition precautions from the docs being applied.
+
+    property Item delegate: parent
+
+    readonly property HNumberAnimation opacityFixer: HNumberAnimation {
+        target: delegate
+        property: "opacity"
+        from: delegate.opacity
+        to: 1
+    }
+
+    readonly property HNumberAnimation scaleFixer: HNumberAnimation {
+        target: delegate
+        property: "scale"
+        from: delegate.scale
+        to: 1
+    }
+
+
+    interval: theme.animationDuration * 2
+    running: true
+    onTriggered: {
+        // if (delegate.opacity < 1 || delegate.scale < 1) print(delegate)
+        if (delegate.opacity < 1) opacityFixer.start()
+        if (delegate.scale < 1) scaleFixer.start()
+    }
+}