Bug 11437 jar packager: no error message but buttons disabled
20020314 on the 'jar manifest' wizard page, if you select to use existing manifest file there's no error message but next and finish are disabled user should be informed what to do to make the wizard happy
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/jarpackager/JarManifestWizardPage.java
} else if (!fJarPackage.isMainClassValid(getContainer())) {
			
			fJarPackage.setMainClass(null);
			fMainClassText.setText(fJarPackage.getMainClassName());
		}
	}
	protected void handleSealPackagesDetailsButtonPressed() {
		SelectionDialog dialog= createPackageDialog(fJarPackage.getPackagesForSelectedResources());
		dialog.setTitle(JarPackagerMessages.getString("JarManifestWizardPage.sealedPackagesSelectionDialog.title")); 
		dialog.setMessage(JarPackagerMessages.getString("JarManifestWizardPage.sealedPackagesSelectionDialog.message")); 
		dialog.setInitialSelections(fJarPackage.getPackagesToSeal());
		if (dialog.open() == dialog.OK)
			fJarPackage.setPackagesToSeal(getPackagesFromDialog(dialog));
		updateSealingInfo();
	}
	protected void handleUnSealPackagesDetailsButtonPressed() {
		SelectionDialog dialog= createPackageDialog(fJarPackage.getPackagesForSelectedResources());
		dialog.setTitle(JarPackagerMessages.getString("JarManifestWizardPage.unsealedPackagesSelectionDialog.title")); 
		dialog.setMessage(JarPackagerMessages.getString("JarManifestWizardPage.unsealedPackagesSelectionDialog.message")); 
		dialog.setInitialSelections(fJarPackage.getPackagesToUnseal());
		if (dialog.open() == dialog.OK)
			fJarPackage.setPackagesToUnseal(getPackagesFromDialog(dialog));
		updateSealingInfo();
	}
	/**
	 * Updates the enable state of this page's controls. Subclasses may extend.
	 */
	protected void updateEnableState() {
		boolean generate= fGenerateManifestRadioButton.getSelection();
		boolean save= generate && fSaveManifestCheckbox.getSelection();