#159 Update Validate

[Andrew Osintsev]

public ValidationError Validate()
{
if (_validators == null) return null;
ValidationError result = null;
foreach (var validatable in _validators)

instead

public ValidationError Validate()
{
ValidationError result = null;
if (_validators == null) return null;
foreach (var validatable in _validators)

[Andrew Osintsev]

[r751]