Throwing an exception when there are no weak reactions

[Artyom Makhno]

Hello!

What about throwing an exception when you try to add a library with an argument "Weak" but there are no reactions with the flag "w" in a file?

I created own library with weak reactions only and forget about adding the flag "w" to every reaction. The result was "0 reactions in my library". In my opinion, the end user should deal with such situations in a better way than debugging everything.

Thank you,
Artem