Show the user's id or a room's canonical alias (if set) in invites

This should prevent the easiest way of masquerading, and provide an \
important identifier for rooms. Note that *only* the room canonical
alias is shown, if it's not set then it's just the display name. This is
intentional as regular users rarely interact with room IDs, but they can
still check it elsewhere in NeoChat.

src/app/qml/InvitationView.qml

@@ -52,6 +52,15 @@ ColumnLayout {
                 Layout.alignment: Qt.AlignHCenter
             }
 
+            Kirigami.SelectableLabel {
+                Layout.fillWidth: true
+                font: Kirigami.Theme.smallFont
+                textFormat: TextEdit.PlainText
+                visible: root.currentRoom && root.currentRoom.canonicalAlias
+                text: root.currentRoom && root.currentRoom.canonicalAlias ? root.currentRoom.canonicalAlias : ""
+                color: Kirigami.Theme.disabledTextColor
+            }
+
             Kirigami.Heading {
                 text: root.currentRoom.displayName
 
@@ -70,7 +79,14 @@ ColumnLayout {
             spacing: Kirigami.Units.smallSpacing
 
             Kirigami.Heading {
-                text: root.currentRoom.displayName
+                text: root.invitingMember.displayName
+
+                Layout.alignment: Qt.AlignHCenter
+            }
+
+            QQC2.Label {
+                text: root.invitingMember.id
+                color: Kirigami.Theme.disabledTextColor
 
                 Layout.alignment: Qt.AlignHCenter
             }

src/libneochat/neochatroom.cpp

@@ -1674,6 +1674,10 @@ void NeoChatRoom::setRoomState(const QString &type, const QString &stateKey, con
 
 NeochatRoomMember *NeoChatRoom::qmlSafeMember(const QString &memberId)
 {
+    if (memberId.isEmpty()) {
+        return nullptr;
+    }
+
     if (!m_memberObjects.contains(memberId)) {
         auto member = m_memberObjects.emplace(memberId, std::make_unique<NeochatRoomMember>(this, memberId)).first->second.get();
         QQmlEngine::setObjectOwnership(member, QQmlEngine::CppOwnership);