Cleanup connection handling in QML

Consistently pass connection objects to files that need them instead of randomly using Controller.activeConnection in some of them

src/qml/Component/ChatBox/ChatBox.qml

@@ -36,6 +36,8 @@ ColumnLayout {
      */
     required property NeoChatRoom currentRoom
 
+    required property NeoChatConnection connection
+
     /**
      * @brief A message has been sent from the chat bar.
      */
@@ -62,6 +64,8 @@ ColumnLayout {
     ChatBar {
         id: chatBar
 
+        connection: root.connection
+
         visible: root.currentRoom.canSendEvent("m.room.message")
 
         Layout.fillWidth: true