Remove unnecessary null pointer checks

[elfring]

Extra null pointer checks are not needed like in the function “InputBuffer::incrementalHistorySearch”.

[ViralTaco]

I know you asked in 2018 but if you want that make a pull request. I'm beginning the process of refactoring the whole framework. I was working on a version with windows support but at this point I just can't handle it anymore, there's linux for windows now, too… So yeah…