You are using tabs, please use spaces. Check how it looks:
https://github.com/topilski/robomongo/blob/master/src/robomongo/core/domain/MongoDatabase.cpp#L103
https://github.com/topilski/robomongo/blob/master/src/robomongo/core/domain/MongoDatabase.cpp#L105

Check that the rest of the file is indented as needed.

This rule documented here:
https://github.com/paralect/robomongo/wiki/Robomongo-Coding-Style#wiki-no-tabs