Ensure roomId are not rendered in the UI.

Add preview to see the effect.
Use RoomAvatar data fallback everywhere, to not use roomId (`!` char) for the avatar initial, but rather `#`.

features/preferences/impl/src/main/kotlin/io/element/android/features/preferences/impl/notifications/edit/EditDefaultNotificationSettingStateProvider.kt

@@ -42,16 +42,21 @@ private fun anEditDefaultNotificationSettingsState(
 ) = EditDefaultNotificationSettingState(
     isOneToOne = isOneToOne,
     mode = RoomNotificationMode.MENTIONS_AND_KEYWORDS_ONLY,
-    roomsWithUserDefinedMode = persistentListOf(aRoomSummary()),
+    roomsWithUserDefinedMode = persistentListOf(
+        aRoomSummary("Room"),
+        aRoomSummary(null),
+    ),
     changeNotificationSettingAction = changeNotificationSettingAction,
     displayMentionsOnlyDisclaimer = displayMentionsOnlyDisclaimer,
     eventSink = {}
 )
 
-private fun aRoomSummary() = RoomSummary.Filled(
+private fun aRoomSummary(
+    name: String?,
+) = RoomSummary.Filled(
     aRoomSummaryDetails(
         roomId = RoomId("!roomId:domain"),
-        name = "Room",
+        name = name,
         avatarUrl = null,
         isDirect = false,
         lastMessage = null,

features/preferences/impl/src/main/kotlin/io/element/android/features/preferences/impl/notifications/edit/EditDefaultNotificationSettingView.kt

@@ -21,6 +21,7 @@ import androidx.compose.foundation.selection.selectableGroup
 import androidx.compose.runtime.Composable
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.res.stringResource
+import androidx.compose.ui.text.font.FontStyle
 import androidx.compose.ui.tooling.preview.PreviewParameter
 import io.element.android.features.preferences.impl.R
 import io.element.android.libraries.designsystem.components.async.AsyncActionView
@@ -100,7 +101,11 @@ fun EditDefaultNotificationSettingView(
                     )
                     ListItem(
                         headlineContent = {
-                            Text(text = summary.details.name)
+                            val roomName = summary.details.name
+                            Text(
+                                text = roomName ?: stringResource(id = CommonStrings.common_no_room_name),
+                                fontStyle = FontStyle.Italic.takeIf { roomName == null }
+                            )
                         },
                         supportingContent = {
                             Text(text = subtitle)