fix: multi-displays, displays changed, switch idx (#9006)

Use init display index as the primary index.

But when displays changed, the primary display may also changes.

No need to change the old primary index.
But we need to make sure that the old primary index does not exceed the display number.

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

flutter/lib/models/model.dart

@@ -1003,14 +1003,15 @@ class FfiModel with ChangeNotifier {
             // Notify to switch display
             msgBox(sessionId, 'custom-nook-nocancel-hasclose-info', 'Prompt',
                 'display_is_plugged_out_msg', '', parent.target!.dialogManager);
-            final newDisplay = pi.primaryDisplay == kInvalidDisplayIndex
-                ? 0
-                : pi.primaryDisplay;
-            final displays = newDisplay;
+            final isPeerPrimaryDisplayValid =
+                pi.primaryDisplay == kInvalidDisplayIndex ||
+                    pi.primaryDisplay >= pi.displays.length;
+            final newDisplay =
+                isPeerPrimaryDisplayValid ? 0 : pi.primaryDisplay;
             bind.sessionSwitchDisplay(
               isDesktop: isDesktop,
               sessionId: sessionId,
-              value: Int32List.fromList([displays]),
+              value: Int32List.fromList([newDisplay]),
             );
 
             if (_pi.isSupportMultiUiSession) {