Building VarCheckHiiLib fails on my clang 19.1.6 setup with the error variable 'Status' is used uninitialized whenever 'if' condition is false due to the DispatchHandle != NULL test. Calling this function with a NULL handle makes no sense, so move the test to the function entry and return failure if appropriate. Signed-off-by: Leif Lindholm <leif.lindholm@oss.qualcomm.com>