[metacity] place: suppress logically dead code defects

[Alberts Muktupāvels <muktupavels src gnome org>]

commit 4d4671e569a5399a69a07147ac2a30384e3377dd
Author: Alberts Muktupāvels <alberts muktupavels gmail com>
Date:   Sun Mar 14 20:45:06 2021 +0200

    place: suppress logically dead code defects
    
    Both enumeration values are handled outside of switch.
    
    Coverity CID: #1445661

 src/core/place.c | 6 ++++++
 1 file changed, 6 insertions(+)
---
diff --git a/src/core/place.c b/src/core/place.c
index cd45f12f8..f60da6b0b 100644
--- a/src/core/place.c
+++ b/src/core/place.c
@@ -724,8 +724,14 @@ find_preferred_position (MetaWindow *window,
             *new_y += work_area.y;
             break;
 
+          /* coverity[dead_error_line] */
           case META_PLACEMENT_MODE_SMART:
+            g_assert_not_reached ();
+            break;
+
+          /* coverity[dead_error_line] */
           case META_PLACEMENT_MODE_CASCADE:
+            g_assert_not_reached ();
             break;
 
           default: