better code (ganfra's review)

matrix-sdk-android/src/main/java/im/vector/matrix/android/api/session/room/timeline/TimelineEvent.kt

@@ -56,13 +56,13 @@ data class TimelineEvent(
 
     fun getDisambiguatedDisplayName(): String {
         return if (isUniqueDisplayName) {
-            senderName ?: root.senderId
+            senderName
         } else {
-            senderName?.let {
+            senderName?.let { name ->
-                it + " (" + root.senderId + ")"
+                "$name (${root.senderId})"
+            }
         }
                 ?: root.senderId
-        }
                 ?: ""
     }