Fix crash when clicking fast on back key on the Labs screen.

features/preferences/impl/src/main/kotlin/io/element/android/features/preferences/impl/PreferencesFlowNode.kt

@@ -190,7 +190,12 @@ class PreferencesFlowNode(
                 createNode<DeveloperSettingsNode>(buildContext, listOf(developerSettingsCallback))
             }
             NavTarget.Labs -> {
-                createNode<LabsNode>(buildContext)
+                val callback = object : LabsNode.Callback {
+                    override fun onDone() {
+                        backstack.pop()
+                    }
+                }
+                createNode<LabsNode>(buildContext, listOf(callback))
             }
             NavTarget.About -> {
                 val callback = object : AboutNode.Callback {

features/preferences/impl/src/main/kotlin/io/element/android/features/preferences/impl/labs/LabsNode.kt

@@ -16,6 +16,7 @@ import com.bumble.appyx.core.plugin.Plugin
 import dev.zacsweers.metro.Assisted
 import dev.zacsweers.metro.AssistedInject
 import io.element.android.annotations.ContributesNode
+import io.element.android.libraries.architecture.callback
 import io.element.android.libraries.di.SessionScope
 
 @ContributesNode(SessionScope::class)
@@ -25,9 +26,18 @@ class LabsNode(
     @Assisted plugins: List<Plugin>,
     private val presenter: LabsPresenter,
 ) : Node(buildContext, plugins = plugins) {
+    interface Callback : Plugin {
+        fun onDone()
+    }
+
+    val callback: Callback = callback()
+
     @Composable
     override fun View(modifier: Modifier) {
         val state = presenter.present()
-        LabsView(state = state, onBack = ::navigateUp)
+        LabsView(
+            state = state,
+            onBack = callback::onDone,
+        )
     }
 }