fix: web, reset cursor on disconn, back to main page (#9192)

Signed-off-by: fufesou <linlong1266@gmail.com>

flutter/lib/models/input_model.dart

@@ -784,7 +784,7 @@ class InputModel {
     if (!isInputSourceFlutter) {
       bind.sessionEnterOrLeave(sessionId: sessionId, enter: enter);
     }
-    if (enter) {
+    if (!isWeb && enter) {
       bind.setCurSessionId(sessionId: sessionId);
     }
   }

flutter/lib/models/model.dart

@@ -2183,6 +2183,7 @@ class CursorModel with ChangeNotifier {
       debugPrint("deleting cursor with key $k");
       deleteCustomCursor(k);
     }
+    resetSystemCursor();
   }
 
   trySetRemoteWindowCoords() {