[command-completion] EA-1709598 read action to get editor

GitOrigin-RevId: 767999a84f5ede334c235b52910f33fd9ae44213

platform/lang-impl/src/com/intellij/codeInsight/completion/command/CommandCompletionService.kt

@@ -358,7 +358,8 @@ private class CommandCompletionHighlightingListener(
   }
 
   override fun dispose() {
-    clear(lookup.editor)
+    val lookupEditor = runReadAction { lookup.editor }
+    clear(lookupEditor)
   }
 }