comctl32 / ComboEx - Wrong initial selection on first focus

reactos-bootcd-0.4.15-dev-7434-g8b5c5fb-x86-gcc-lin-dbg

Found while testing CORE-19407 patches : 

• Open Explorer (My Computer)
• In address bar click in the middle of the text of the address bar ComboEx : 
• Half of the text gets selected 

• Click again next character
• Correct behavior (carret at the click position, no selection)

• Maybe related to CORE-19423 (but different cause / effects)
• Wine is not affected (Wine 8.0.2 / Ubuntu) as the root cause are extra WM_MOUSEMOVE message, specific to ReactOS as per CORE-8394

Cause : EDIT_WM_MouseMove affecting selection set on EDIT_WM_LButtonDown and as a consequence of CORE-8394

Something is affecting es->selection_start which is correct after EDIT_WM_LButtonDown and back to "0" when the undue EDIT_WM_MouseMove is triggered 

See: ROS-screen0.webm