[Fuzzing] [adamsitnik] [NRBF] Fix bugs discovered by the fuzzer

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Job completed in 37 minutes 21 seconds.
dotnet/runtime#107368

ERROR: System.Exception: Fuzzer 'NrbfDecoder' not found. Available fuzzers: AssemblyNameInfoFuzzer, Base64Fuzzer, Base64UrlFuzzer, HttpHeadersFuzzer, JsonDocumentFuzzer, SearchValuesByteCharFuzzer, SearchValuesStringFuzzer, TextEncodingFuzzer, TypeNameFuzzer, UTF8Fuzzer
   at Runner.Jobs.FuzzLibrariesJob.RunFuzzersAsync(String fuzzerNamePattern) in D:\a\runtime-utils\runtime-utils\Runner\Jobs\FuzzLibrariesJob.cs:line 83
   at Runner.Jobs.FuzzLibrariesJob.RunJobCoreAsync() in D:\a\runtime-utils\runtime-utils\Runner\Jobs\FuzzLibrariesJob.cs:line 34
   at Runner.JobBase.RunJobAsync() in D:\a\runtime-utils\runtime-utils\Runner\JobBase.cs:line 116

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