Add a check in non-debug mode for a T_NONE class

[jhawthorn]

Although a crash could occur anywhere, one of the most common symptoms we see from getting a reference to a garbage collected object is crashing while attempting to call a method on it.

These crashes usually occur when trying to perform an rb_id_table_lookup in the "class" cc_tbl, where the class is usually another garbage collected object, because the freelist is stored in the class pointer. This of course isn't guaranteed to happen, as it only works for T_NONE.

This commit aims to have a better error message in this case, in hopes of having a better grouping of errors and to give a better hint to those investigating and triaging crashes.

Example output:

ptr = Fiddle.dlwrap(Object.new)
GC.start
Fiddle.dlunwrap(ptr).to_s

./test.rb:9: [BUG] attempted to search method 'to_s' on a garbage collected object
ruby 3.5.0dev (2025-05-05T16:29:43Z call_t_none_assert.. 7b419c752b) +PRISM [arm64-darwin24]

-- Crash Report log information --------------------------------------------

[samuel-williams-shopify]

Could we consider upstreaming this change? LGTM.