Dynamic rows loses old input at form error

Observed in Administration -> General -> Macros. This might be an issue everywhere, where $.fn.dynamicRows are used. Please check.

Steps to reproduce:

• Open Administration -> General -> Macros
• Have two macro in there.
• Remove first macro and append one incorrect macro.
• Submit.
• Observed: you are presented with correct form and error message
• Now remove first row again and append incorrect macro again.
• Submit:
• Observed: the first row item has vanished, you are presented with error message
• Expected: Old form should be correct.