S7_base_class not compatible with S4_class()

[jtlandis]

When register_S4_method() gets called, but a S7_base_class is in the signature, it seems to fail because vanilla S7_base_class does not have any properties:

S7/R/method-register.R

Lines 242 to 247 in b5cf389

	S4_class <- function(x, S4_env) {
	if (is_base_class(x)) {
	x@name
	} else if (is_S4_class(x)) {
	x
	} else if (is_class(x) || is_S3_class(x)) {

 str(S7::class_list)
#> <S7_base_class>: <list>
S7::class_list@name
#> Error in S7::class_list@name: no applicable method for `@` applied to an object of class "S7_base_class"

^{Created on 2024-10-20 with reprex v2.1.1}