Amend "effects/private: Merge two state machines into one with substates"

This commit amends 9897afa5.

Changes were pushed to the wrong branch, so the MR got merged not in its
final state.

(cherry picked from commit 3af565b6)

src/effects/private/qml/WindowHeapDelegate.qml

@@ -228,6 +228,13 @@ Item {
                     ? (thumb.activeHidden ? 0 : effect.partialActivationFactor)
                     : (thumb.activeHidden ? 1 - effect.partialActivationFactor : 1)
             }
+            PropertyChanges {
+                target: thumbSource
+                x: 0
+                y: 0
+                width: thumb.width
+                height: thumb.height
+            }
             PropertyChanges {
                 target: icon
                 opacity: effect.partialActivationFactor