Remove Nullable Disable from ICC Code

[stefannikolei]

Removed the nullable disable from the icc Code (And one Tiff). Most parts could be solved relative easily. There are also some parts were the bang operator had to be used.

Prerequisites

• [x] I have written a descriptive pull-request title
• [x] I have verified that there are no overlapping pull-requests open
• [x] I have verified that I am following the existing coding patterns and practice as demonstrated in the repository. These follow strict Stylecop rules :cop:.
• [x] I have provided test coverage for my change (where applicable)