[rd debugger] Do not compute children when parent scope already cancelled

it caused ClosedSendChannelException in tests

GitOrigin-RevId: 89492bc4af7353c676115eee2a7cb2f37afaa127

platform/xdebugger-impl/backend/src/com/intellij/platform/debugger/impl/backend/BackendXValueApi.kt

@@ -184,7 +184,7 @@ internal fun computeContainerChildren(
 
   return channelFlow {
     parentCs.awaitCancellationAndInvoke {
-      close()
+      rawEvents.close()
     }
     val addNextChildrenCallbackHandler = AddNextChildrenCallbackHandler(this@channelFlow)
 
@@ -224,16 +224,12 @@ internal fun computeContainerChildren(
       }
     }
 
-    launch {
+    try {
+      xValueContainer.computeChildren(xCompositeBridgeNode)
       for (event in rawEvents) {
         send(event.convertToRpcEvent(parentCs, session))
       }
     }
-
-    try {
-      xValueContainer.computeChildren(xCompositeBridgeNode)
-      awaitClose()
-    }
     finally {
       xCompositeBridgeNode.obsolete = true
     }