Handle all value_t enumerators in has_no_children() (#5770)

2026-10-07: add the scalar enum labels already handled by the default
branch so -Werror=switch-enum builds succeed. Keep the existing behavior
and synchronize the generated single header.

Signed-off-by: fhgffy <102001626+fhgffy@users.noreply.github.com>

single_include/nlohmann/json.hpp

@@ -27872,6 +27872,14 @@ private:
                     return v.m_data.m_value.array->empty();
                 case value_t::object:
                     return v.m_data.m_value.object->empty();
+                case value_t::null:
+                case value_t::string:
+                case value_t::boolean:
+                case value_t::number_integer:
+                case value_t::number_unsigned:
+                case value_t::number_float:
+                case value_t::binary:
+                case value_t::discarded:
                 default:
                     return true;
             }