COMP: NIFTI Coverity buffer not null terminated
Fixed defects like the following:
If the buffer is treated as a null terminated string in later operations, a buffer overflow or over-read may occur.
In vtkNIFTIImageWriter::GenerateHeader(vtkInformation *, bool): The string buffer may not have a null terminator if the source string's length is equal to the buffer size (CWE-170)