fix: pop backstack crash in certain scenarios

app/src/main/java/com/zaneschepke/wireguardautotunnel/MainActivity.kt

@@ -55,7 +55,6 @@ import androidx.core.splashscreen.SplashScreen.Companion.installSplashScreen
 import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import androidx.lifecycle.lifecycleScope
 import androidx.lifecycle.viewmodel.navigation3.rememberViewModelStoreNavEntryDecorator
-import androidx.navigation3.runtime.NavKey
 import androidx.navigation3.runtime.entryProvider
 import androidx.navigation3.runtime.rememberNavBackStack
 import androidx.navigation3.runtime.rememberSaveableStateHolderNavEntryDecorator
@@ -185,10 +184,12 @@ class MainActivity : AppCompatActivity() {
             var previousRoute by remember { mutableStateOf<Route?>(null) }
 
             val navController =
-                rememberNavController<NavKey>(backStack, uiState.isLocationDisclosureShown) {
-                    previousKey ->
-                    previousRoute = previousKey as? Route
-                }
+                rememberNavController(
+                    backStack,
+                    uiState.isLocationDisclosureShown,
+                    onChange = { previousKey -> previousRoute = previousKey as? Route },
+                    onExitApp = { finish() },
+                )
 
             val vpnActivity =
                 rememberLauncherForActivityResult(

app/src/main/java/com/zaneschepke/wireguardautotunnel/ui/navigation/NavController.kt

@@ -7,6 +7,7 @@ class NavController(
     private val backStack: NavBackStack<NavKey>,
     private val isDisclosureShown: Boolean,
     private val onChange: (previous: NavKey?) -> Unit = {},
+    private val onExitApp: () -> Unit = {},
 ) {
     fun push(route: NavKey) {
         onChange(currentRoute)
@@ -14,12 +15,13 @@ class NavController(
     }
 
     fun pop(): Boolean {
-        if (currentRoute != null) {
-            onChange(currentRoute)
-            backStack.removeLastOrNull()
+        if (!canPop) {
+            onExitApp()
             return true
         }
-        return false
+        onChange(currentRoute)
+        backStack.removeLastOrNull()
+        return true
     }
 
     fun popUpTo(route: NavKey) {

app/src/main/java/com/zaneschepke/wireguardautotunnel/ui/navigation/functions/rememberNavController.kt

@@ -7,12 +7,13 @@ import androidx.navigation3.runtime.NavKey
 import com.zaneschepke.wireguardautotunnel.ui.navigation.NavController
 
 @Composable
-fun <T : NavKey> rememberNavController(
+fun rememberNavController(
     backStack: NavBackStack<NavKey>,
     isDisclosureShown: Boolean,
     onChange: (NavKey?) -> Unit = {},
+    onExitApp: () -> Unit = {},
 ): NavController {
-    return remember(backStack, onChange, isDisclosureShown) {
-        NavController(backStack, isDisclosureShown, onChange)
+    return remember(backStack, isDisclosureShown, onChange, onExitApp) {
+        NavController(backStack, isDisclosureShown, onChange, onExitApp)
     }
 }