Fix notNull annotation and fix test accordingly
What does this MR do (summary)?
Fixes a broken @NotNull annotation
What changes have you made (detailed)?
Fix import, fix test
Does this MR meet the acceptance criteria?
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The main application was run to make sure the server still runs without errors. -
Tests were written to verify the behaviour of this code. -
Javadoc and other comments were added to make the code understandable. -
The code adheres to the style guidelines.