* Avoid setting .rest for Locked_sexp_true/false with malformed SEXPs.
When FRED puts a `true` in the middle of a list of arguments, it wraps it in a nested list as `(true)`, because it's technically an operator; however, if someone writes a SEXP by hand, they could easily forget to do this, and in such cases, this causes `Locked_sexp_true` to be inserted into the middle of the list. If it's not the last element of the list, it will then have its `.rest` attribute set to the next node in the list. If this is a temporary SEXP (i.e. from Lua's `runSEXP()` function), this used to be a temporary problem, but PR #4088 changed the global search for any node with `.rest` set to the node being freed to require an explicit parent node. This means that `Locked_sexp_true.rest` remains set to a freed node, which can cause further issues. If such a malformed SEXP *isn't* temporary it can cause even more issues, even pre-#4088.
This commit changes `get_sexp()` so that if it detects `true` or `false` in the middle of a list (and not a single-element list), it will put it into a single-element sub-list, hopefully preventing any modification of `Locked_sexp_true` or `Locked_sexp_false`, as giving a `Warning`. This should cause it to behave as though `true` or `false` was actually `(true)` or `(false)`, respectively, and therefore run as expected.
* Add comment and remove unused variable declaration.
Thanks to @PhantomHoover for the wording on the comment.
MageKing17
acaa93a9d2