frontend: catch tracebacks when rendering invalid modules
    
    Fix #1752
    
    We have some modules with invalid modulemd YAML files in our
    database. The validation used to be rather benevolent in the initial
    implementations. With this, we can print a user-friendly for such
    modules. At this moment, there are 57 modules in the Fedora Copr
    instance, that cannot be parsed. One of them because of
    
        Hint: Unexpected scalar outside of map. [line 71 col 11]
    
    The rest of them because of
    
        Hint: Module license is missing