tests/misc_tests.c: Address clang-tidy 18 warning EnumCastOutOfRange
clang-tidy output was:
> [..]/libexpat/expat/tests/misc_tests.c:112:23: note: The value '-1' provided to the cast expression is not in the valid range of values for 'XML_Error'
> 112 | if (XML_ErrorString((enum XML_Error) - 1) != NULL)
> | ^~~~~~~~~~~~~~~~~~~~
> [..]/libexpat/expat/tests/misc_tests.c:114:23: error: The value '100' provided to the cast expression is not in the valid range of values for 'XML_Error' [clang-analyzer-optin.core.EnumCastOutOfRange,-warnings-as-errors]
> 114 | if (XML_ErrorString((enum XML_Error)100) != NULL)
> | ^~~~~~~~~~~~~~~~~~~
1 file changed
