[Navigation] Prevent pop on root [Android] (#8)

Fix issue where it would be possible to pop the root destination, leading to an empty navhost

navigation/common/src/androidMain/kotlin/com/mirego/pilot/navigation/compose/PilotNavControllerNavigationListener.kt

@@ -13,7 +13,9 @@ public open class PilotNavControllerNavigationListener<ROUTE : PilotNavigationRo
     }
 
     override fun pop() {
-        navController.popBackStack()
+        if (navController.previousBackStackEntry != null) {
+            navController.popBackStack()
+        }
     }
 
     override fun popTo(route: ROUTE, inclusive: Boolean) {