Desktop: Fix bad selection/paint after drag selecting around window

Caught by accident when automating a test case. Yay! Same root cause
as the fix in 7668b93 - clearing selection can change what icons are
cached. Similar fix.

This regressed in 22975d4, so new in 1.6

Author: inexorabletash

src/desktop/main.s

@@ -5351,6 +5351,7 @@ END_PARAM_BLOCK
         jsr     ExtendSelectionModifierDown
         bmi     :+
 clear:  jsr     ClearSelection
+        CALL    CacheWindowIconList, A=window_id
 :
 
         ;; --------------------------------------------------

tests/desktop/repaints.lua

@@ -174,7 +174,7 @@ end)
   window.
 ]]
 test.Step(
-  "drag select on desktop doesn't select file icons - after icon click",
+  "drag select on desktop doesn't select file icons - with file icon selection",
   function()
     a2d.SelectPath("/A2.DESKTOP/READ.ME")
     a2d.MoveWindowBy(40, 30)
@@ -184,8 +184,6 @@ test.Step(
              rect[3] + 20, rect[4] + 10)
     a2d.InMouseKeysMode(function(m) m.Home() end)
 
-    -- BUG: Bad paint inside window!!!
-
     test.Snap("verify no mispaint")
     test.ExpectEquals(#a2d.GetSelectedIcons(), 0, "nothing should be selected")
 end)