Fix color of room page background

It should be a View so use the View colorSet.

imports/NeoChat/Component/FancyEffectsContainer.qml

@@ -10,7 +10,7 @@ import QtQuick.Particles 2.12
 
 import org.kde.kirigami 2.4 as Kirigami
 
-Item {
+Rectangle {
     id: item
     property bool enabled: false
     property int effectInterval: Kirigami.Units.veryLongDuration*10;
@@ -29,6 +29,11 @@ Item {
         fireworksTimer.start()
     }
 
+    // backgroundColor
+    color: Kirigami.Theme.backgroundColor
+    Kirigami.Theme.colorSet: Kirigami.Theme.View
+    Kirigami.Theme.inherit: true
+
     // Confetti
 
     Timer {