Null values for float, int and other numericals

Good day, and thanks for reading.
I used float parameter of Animator component to control wich animation to play and such.
But now i need to use sabe script for alot of same onjects, some of wich may not have that float declared in animatorcontroler.
So question is - if i use GetFloat from animator and it doesnt exist, what will i get? It wont agree to compare to null because undeclared float is not a null and allweys returns true.
But what whill i get as a return from GetFloat if float i`m looking for is not even there?

            if(Anim.GetFloat("CurrentSpeed") //Some way to find if this float exists in current animatorcontroller//)  
           {
                Anim.SetFloat("CurrentSpeed", Speed); // Set float to current speed
            }

Thanks)

The parameter array returned will have all the defined parameters. You can check against this list to see if your parameter is defined or not.