message: Fix nullptr access
  If no test suite has been set and we fail in a test, then `tc.m_test_suite` is `nullptr`.
diff: @@ -1442,7 +1442,7 @@ namespace detail
  forDebugConsole += d1;
  forDebugConsole += d2;
  }
  - if(tc.m_test_suite[0] != '\0') {
  + if(tc.m_test_suite && tc.m_test_suite[0] != '\0') {
  DOCTEST_PRINTF_COLORED(ts1, Color::Yellow);
  DOCTEST_PRINTF_COLORED(ts2, Color::None);
  forDebugConsole += ts1;
  