[pycharm] PY-85546 Fix automatic deselection on show background processes toggle

Merge-request: IJ-MR-182105
Merged-by: David Lysenko <david.lysenko@jetbrains.com>

GitOrigin-RevId: 3059d9543addb56c5ed5c969076fbfec48a2b56e

python/python-process-output/impl/src/com/intellij/python/processOutput/impl/ProcessOutputControllerService.kt

@@ -462,9 +462,15 @@ class ProcessOutputControllerService(
                 }
             }
 
-            processTree.value = buildTree {
+            val newTree = buildTree {
                 buildNodeTree(root)
             }
+
+            if (newTree.isEmpty()) {
+                selectProcess(null)
+            }
+
+            processTree.value = newTree
         }.launchIn(coroutineScope)
     }