The error you see arises when one of the arguments to
eq is either undefined in the current context or is not of a "basic type" (see the last paragraph of this section)
So assuming that
footer.html is a "pratial" template that is associated with other templates which invoke the footer template using the template action you need to ensure that the context passed in to the template invocation contains the
.RunMode value and that the value is of a basic type.