You are using tabs, please use spaces. Check how it looks: 
https://github.com/topilski/robomongo/blob/master/src/robomongo/gui/GuiRegistry.cpp#L60

This rule documented here:
https://github.com/paralect/robomongo/wiki/Robomongo-Coding-Style#wiki-no-tabs

Also apply to this file the following rule:
https://github.com/paralect/robomongo/wiki/Robomongo-Coding-Style#wiki-blank-lines