Cancel delayed progress dialog after busy cursor run

Same as with the other call in the same class, whoever schedules the
progress dialog to be shown after a delay (800 ms) should also make sure
that the dialog doesn't pop-up if the runnable is finished before the
delay has elapsed.

Author: fedejeanne

bundles/org.eclipse.ui.workbench/eclipseui/org/eclipse/ui/internal/progress/ProgressManager.java

@@ -942,13 +942,19 @@ public void busyCursorWhile(final IRunnableWithProgress runnable)
 	 */
 	private void busyCursorWhile(Runnable dialogWaitRunnable, ProgressMonitorJobsDialog dialog) {
 		// Create the job that will open the dialog after a delay.
-		scheduleProgressMonitorJob(dialog);
-		final Display display = PlatformUI.getWorkbench().getDisplay();
-		if (display == null) {
-			return;
+		Job showDialogJob = scheduleProgressMonitorJob(dialog);
+		try {
+			final Display display = PlatformUI.getWorkbench().getDisplay();
+			if (display == null) {
+				return;
+			}
+			// Show a busy cursor until the dialog opens.
+			BusyIndicator.showWhile(display, dialogWaitRunnable);
+		} finally {
+			// In case the dialog hasn't popped up yet, cancel it so it doesn't pop up after
+			// the operation finishes or unwinds with an exception.
+			showDialogJob.cancel();
 		}
-		// Show a busy cursor until the dialog opens.
-		BusyIndicator.showWhile(display, dialogWaitRunnable);
 	}
 
 	/**