Red: REPEND crashes when using TRIM on the target series.

[dockimbel]

The following code crashes the console:

data: "   123   "
repend data [trim data]

If trim is removed, it works as expected.

[dockimbel]

See also https://github.com/red/red/issues/3340

Temporary workaround:

data: "   123   "
append data reduce [trim data]
== "123123"

Minimal code to reproduce the crash:

data: "   123   "
insert tail data reduce [trim data]

Caused by insert not handling properly the case of same string series used for both arguments.

[dockimbel]

Crash happens in string/alter in:

if mode = MODE_INSERT [
    move-memory             
        (as byte-ptr! s1/offset) + h1 + offset + size
        (as byte-ptr! s1/offset) + h1 + offset
        (as-integer s1/tail - s1/offset) - h1
]

The last argument to move-memory is negative (-6 in above case), because trim data makes the tail data reference become "past-end".

The fix for this issue should be part of the general solution for handling past-end series internally.

[hiiamboris]

https://github.com/red/red/pull/4097

[dockimbel]

@hiiamboris I will process the pending PRs once the lexer branch is merged into master.