Add observer to re-enable link detection when signing out of an account.

Riot/Managers/URLPreviews/URLPreviewService.swift

@@ -33,6 +33,22 @@ class URLPreviewService: NSObject {
     
     /// A persistent store backed by Core Data to reduce network requests
     private let store = URLPreviewStore()
+    /// The observer that re-enables link detection on sign out,
+    private let resetLinkDetectionObserver: Any
+    
+    // MARK: - Setup
+    
+    override init() {
+        resetLinkDetectionObserver = NotificationCenter.default.addObserver(forName: .mxkAccountManagerDidRemoveAccount, object: nil, queue: .main) { _ in
+            MXKAppSettings.standard().enableBubbleComponentLinkDetection = true
+        }
+        
+        super.init()
+    }
+    
+    deinit {
+        NotificationCenter.default.removeObserver(resetLinkDetectionObserver)
+    }
     
     // MARK: - Public