Changed GetPositionFromGuid() to return a nullabe Vector3d

Modified the two places that currently call GetPositionFromGuid() to handle the null value instead of handling an exception. This is more in line with RemoteTechologiiesGroup "codiing style" to not throw execptions where possible.
I'm not sure that travis builds the code in release mode. I think we've to change the `xbuild` call to `xbuild /p:Configuration=Release` but i'm not so familiar with `xbuild`