Bug 55340 Documentation (Javadoc) location selector does not show up with ZIP files
When having a ZIP (not JAR) file included as library there can no documentation location be selected on its properties page. When I rename the file to "*.jar" then it works.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/preferences/JavadocConfigurationPropertyPage.java
private JavadocConfigurationBlock fJavadocConfigurationBlock;
	public JavadocConfigurationPropertyPage() {
	}
	/**
	 * @see org.eclipse.jface.dialogs.IDialogPage#createControl(org.eclipse.swt.widgets.Composite)
	 */
	public void createControl(Composite parent) {
		IJavaElement elem= getJavaElement();
		if (elem instanceof IPackageFragmentRoot)
			setDescription(PreferencesMessages.getString("JavadocConfigurationPropertyPage.IsPackageFragmentRoot.description")); 
		else if (elem instanceof IJavaProject)
			setDescription(PreferencesMessages.getString("JavadocConfigurationPropertyPage.IsJavaProject.description")); 
		else
			setDescription(PreferencesMessages.getString("JavadocConfigurationPropertyPage.IsIncorrectElement.description")); 
		super.createControl(parent);
		WorkbenchHelp.setHelp(getControl(), IJavaHelpContextIds.JAVADOC_CONFIGURATION_PROPERTY_PAGE);
	}
	/*
	 * @see PreferencePage#createContents(Composite)
	 */
	protected Control createContents(Composite parent) {
		
		IJavaElement elem= getJavaElement();
		
		URL initialLocation= null;
		if (elem != null) {
			try {
				initialLocation= JavaUI.getJavadocBaseLocation(elem);
			} catch (JavaModelException e) {