message: Add "empty_map" unit tests for rdcflatmap
  Validate expected behaviour on an empty sorted and unsorted container
  begin() == end()
  find(*) == end()
  lower_bound(*) == 0
  upper_bound(*) == 0
diff: @@ -2291,6 +2291,21 @@ TEST_CASE("Test flatmap type", "[basictypes][flatmap]")
  it = test.upper_bound(8);
  CHECK(it == test.end());
  };
  +
  + SECTION("empty_map")
  + {
  + rdcflatmap<uint32_t, uint32_t> unsorted;
  + CHECK(unsorted.begin() == unsorted.end());
  + CHECK(unsorted.find(0) == unsorted.end());
  + CHECK(unsorted.lower_bound(1) == 0);
  + CHECK(unsorted.upper_bound(2) == 0);
  +
  + rdcflatmap<uint32_t, uint32_t, 0> sorted;
  + CHECK(sorted.begin() == sorted.end());
  + CHECK(sorted.find(0) == sorted.end());
  + CHECK(sorted.lower_bound(1) == 0);
  + CHECK(sorted.upper_bound(2) == 0);
  + }
  };
  union foo
  