Bug 573098 - Switching perspective gives ClassCastException

Change-Id: Iccbdeb967eea0488c2db70b4c35bd4d3cfc7a0b2
Signed-off-by: Kalyan Prasad Tatavarthi <kalyan_prasad@in.ibm.com>
Reviewed-on: https://git.eclipse.org/r/c/platform/eclipse.platform.ui/+/179715
Reviewed-by: Sravan Kumar Lakkimsetti <sravankumarl@in.ibm.com>

bundles/org.eclipse.ui.workbench/Eclipse UI/org/eclipse/ui/internal/CoolBarToTrimManager.java

diff --git a/bundles/org.eclipse.ui.workbench/Eclipse UI/org/eclipse/ui/internal/CoolBarToTrimManager.java b/bundles/org.eclipse.ui.workbench/Eclipse UI/org/eclipse/ui/internal/CoolBarToTrimManager.java
index 5a9e90a..934d534 100644
--- a/bundles/org.eclipse.ui.workbench/Eclipse UI/org/eclipse/ui/internal/CoolBarToTrimManager.java
+++ b/bundles/org.eclipse.ui.workbench/Eclipse UI/org/eclipse/ui/internal/CoolBarToTrimManager.java
@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2011, 2015 IBM Corporation and others.
+ * Copyright (c) 2011, 2021 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
@@ -144,7 +144,8 @@
 				return;
 			}
 
-			MToolBar toolBar = (MToolBar) modelService.find(item.getId(), window);
+			List<MToolBar> toolbars = modelService.findElements(window, item.getId(), MToolBar.class, null);
+			MToolBar toolBar = toolbars.isEmpty() ? null : toolbars.get(0);
 			boolean tbFound = toolBar != null;
 			if (!tbFound) {
 				toolBar = modelService.createModelElement(MToolBar.class);