Revert "Revert "Bug 579048 - Widget is disposed exception from
SWTPartRenderer during unit tests for disposed toolbar entries""

This reverts commit 9b299d1eab3d18864054a56714b5b50e2102b0cd.

Change-Id: Ie4a53f2c9fbf49eefd3aebe230e3b8b8c8e5b0b7
Signed-off-by: Lars Vogel <Lars.Vogel@vogella.com>
Reviewed-on: https://git.eclipse.org/r/c/platform/eclipse.platform.ui/+/191362
Tested-by: Platform Bot <platform-bot@eclipse.org>

bundles/org.eclipse.e4.ui.workbench.renderers.swt/src/org/eclipse/e4/ui/workbench/renderers/swt/SWTPartRenderer.java

diff --git a/bundles/org.eclipse.e4.ui.workbench.renderers.swt/src/org/eclipse/e4/ui/workbench/renderers/swt/SWTPartRenderer.java b/bundles/org.eclipse.e4.ui.workbench.renderers.swt/src/org/eclipse/e4/ui/workbench/renderers/swt/SWTPartRenderer.java
index 02fb269..f5c98b1 100644
--- a/bundles/org.eclipse.e4.ui.workbench.renderers.swt/src/org/eclipse/e4/ui/workbench/renderers/swt/SWTPartRenderer.java
+++ b/bundles/org.eclipse.e4.ui.workbench.renderers.swt/src/org/eclipse/e4/ui/workbench/renderers/swt/SWTPartRenderer.java
@@ -86,8 +86,17 @@
 
 	public void setCSSInfo(MUIElement me, Object widget) {
 		// No SWT widget, nothing to style...
-		if (widget == null)
+		if (widget == null) {
 			return;
+		}
+
+		//
+		if (widget instanceof Widget) {
+			Widget swtWidget = (Widget) widget;
+			if (swtWidget.isDisposed()) {
+				return;
+			}
+		}
 
 		// Set up the CSS Styling parameters; id & class
 		IEclipseContext ctxt = getContext(me);