Bug 117925 [Intro] Misleading exception message in WelcomeEditor.init()
... it says it expects an IFileEditorInput, but it actually checks for WelcomeEditorInput. Suggested patch appended.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/ide/dialogs/WelcomeEditor.java
*/
    private StyledText previousText(StyledText text) {
        int index = 0;
        if (text == null)
            return (StyledText) texts.get(0);
        else
            index = texts.indexOf(text);
        
        if (index == 0)
            return (StyledText) texts.get(texts.size() - 1);
        else
            return (StyledText) texts.get(index - 1);
    }
    /**
     * Returns the current text.
     */
    protected StyledText getCurrentText() {
        return currentText;
    }
    /**
     * Returns the copy action. 
     */
    protected WelcomeEditorCopyAction getCopyAction() {
        return copyAction;
    }
    /**
     * Finds the next link after the current selection.
     */
    private StyleRange findNextLink(StyledText text) {
        if (text == null)