Fixed misleading identations

[kaizerw]

It did not compile with gcc 7.3.0 on Ubuntu 18.04

[jan-dolejsi]

Dear VAL supporters. We've recently managed to re-merge a large fork (see https://github.com/KCL-Planning/VAL/pull/42) and in the process resolved many popular requests, did a major clean-up and made things ready for continuous integration, which will help us safely service future pull requests. We've also setup a build pipeline to democratize binaries for Linux, Windows and MacOS users.

We understand that resolving merge conflicts in your forks may be difficult and will cause some short term pain, but we believe this is a good investment for the future of the project and hope to see your future contributions into this cleaned-up codebase!