Hiding error LUA in a specific macro

First of all, I apologize if I didn't put this topic in the right subforum.
I'd also like to specify that I'm playing on Lordaeron

As a hunter, I use this macro:

/cast Aspect of the Hawk
/cast Aspect of the Viper

This macro is useful to switch from an aspect to another.
However, when I have neither of those macros, the error "Spell is not ready yet" shows up.

I have tried a few commands as UIErrorsFrame:Clear() (or :Hide() + Show()) but the error still shows up.
If I only use UIErrorsFrame:Hide(), all errors are hidden, which I don't want.
I'm not interested in addons that completely stop the error "Spell is not ready yet" from showing up, since this error is bothering me only for this macro, but is useful in other situations.

I'm quite confused as to why UIErrorsFrame:Clear() (or :Hide() + Show()) doesn't work even though it seems to work fine elsewhere.

Can someone please help me on that matter ?