A CRASH when calling offset-to-caret inside a face actor.

[luce80]

Describe the bug
A CRASH when calling offset-to-caret inside a face actor.

To reproduce

view [base "hoi" ON-down [offset-to-caret face event/offset]]

Expected behavior
No crash.

Platform version

>> about/debug
-----------RED & PLATFORM VERSION----------- 
RED: [ branch: "master" tag: #v0.6.4 ahead: 5075 date: 22-Dec-2023/9:07:34 commit: #6cb7d502bcbfae8b00630adee6561909eee2b478 ]
PLATFORM: [ name: "Windows 11" OS: 'Windows arch: 'x86-64 version: 10.0.0 build: 22631 ]
--------------------------------------------

[dockimbel]

Related call stack:

*** Runtime Error 98: assertion failed
*** in file: /C/dev/Red/runtime/datatypes/block.reds
*** at line: 51
***
***   stack: red/block/rs-head 05805228h
***   stack: gui/OS-text-box-metrics 05805228h 0545CBD4h 1
***   stack: ctx||475~text-box-metrics 0545CBC4h 0545CBD4h 1
***   stack: offset-to-caret
***   stack: red/interpreter/call 0545CB94h 04B73884h 0580B428h 0
***   stack: red/interpreter/eval-code 05545938h 0580B468h 0580B468h 0580B3C0h false 00000000h 00000000h 05545938h 0 false
...

There is not enough protection internally in calls to offset-to-caret function against inadequate face objects. In the above case, the face does not have a FACE_OBJ_EXT3 field, so an invalid memory is accessed instead, resulting in a crash.