Use proper shell for modal dialogs

This prevents the dialogs to appear behind the possible opened progress
dialog (or any other modal dialog).

See eclipse-platform/eclipse.platform#1373

ui/org.eclipse.pde.ui/src/org/eclipse/pde/internal/ui/launcher/LaunchTerminationStatusHandler.java

@@ -34,6 +34,7 @@
 import org.eclipse.ui.IWorkbenchPage;
 import org.eclipse.ui.IWorkbenchWindow;
 import org.eclipse.ui.PartInitException;
+import org.eclipse.ui.PlatformUI;
 import org.eclipse.ui.ide.IDE;
 import org.eclipse.ui.internal.views.log.LogView;
 
@@ -60,7 +61,7 @@ private void handleOtherReasonsFoundInLog(final ILaunch launch) {
 			try {
 				File log = LaunchListener.getMostRecentLogFile(launch.getLaunchConfiguration());
 				if (log != null && log.exists()) {
-					MessageDialog dialog = new MessageDialog(PDEPlugin.getActiveWorkbenchShell(), PDEUIMessages.Launcher_error_title, null, // accept the default window icon
+					MessageDialog dialog = new MessageDialog(PlatformUI.getWorkbench().getModalDialogShellProvider().getShell(), PDEUIMessages.Launcher_error_title, null, // accept the default window icon
 							PDEUIMessages.Launcher_error_code13, MessageDialog.ERROR, new String[] {PDEUIMessages.Launcher_error_displayInLogView, PDEUIMessages.Launcher_error_displayInSystemEditor, IDialogConstants.NO_LABEL}, OPEN_IN_ERROR_LOG_VIEW);
 					int dialog_value = dialog.open();
 					if (dialog_value == OPEN_IN_ERROR_LOG_VIEW) {