Fixes backward-compatibility for older modules that return NULL with ModUtil::getModule(), such as the current Profile module.

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | 
| Refs tickets  | https://github.com/zikula-modules/Profile/issues/21
| License       | MIT
| Doc PR        |