Fix T90236: Sculpt automasking failing when the stroke does not start over the mesh

The active geometry element are usually updated by the cursor drawing
code (as they are needed for the cursor preview) and when an sculpt
operator starts. For brushes, this was not happening. This was making
brushes rely by default on the last cursor drawing update, which can
be incorrect if the mouse moved after starting the stroke without
hovering the active geometry.

Reviewed By: JacquesLucke

Maniphest Tasks: T90236

Differential Revision: https://developer.blender.org/D12045

source/blender/editors/sculpt_paint/sculpt.c

@@ -7887,6 +7887,9 @@ static bool sculpt_stroke_test_start(bContext *C, struct wmOperator *op, const f
 
     sculpt_update_cache_invariants(C, sd, ss, op, mouse);
 
+    SculptCursorGeometryInfo sgi;
+    SCULPT_cursor_geometry_info_update(C, &sgi, mouse, false);
+
     SCULPT_undo_push_begin(ob, sculpt_tool_name(sd));
 
     return true;