ui: do not crash if tunnel preparation fails

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

ui/src/main/java/com/wireguard/android/fragment/BaseFragment.kt

@@ -67,12 +67,20 @@ abstract class BaseFragment : Fragment(), OnSelectedTunnelChangedListener {
         val activity = activity ?: return
         activity.lifecycleScope.launch {
             if (Application.getBackend() is GoBackend) {
-                val intent = GoBackend.VpnService.prepare(activity)
-                if (intent != null) {
-                    pendingTunnel = tunnel
-                    pendingTunnelUp = checked
-                    permissionActivityResultLauncher.launch(intent)
-                    return@launch
+                try {
+                    val intent = GoBackend.VpnService.prepare(activity)
+                    if (intent != null) {
+                        pendingTunnel = tunnel
+                        pendingTunnelUp = checked
+                        permissionActivityResultLauncher.launch(intent)
+                        return@launch
+                    }
+                } catch (e: Throwable) {
+                    val message = activity.getString(R.string.error_prepare, ErrorMessages[e])
+                    Snackbar.make(view, message, Snackbar.LENGTH_LONG)
+                        .setAnchorView(view.findViewById(R.id.create_fab))
+                        .show()
+                    Log.e(TAG, message, e)
                 }
             }
             setTunnelStateWithPermissionsResult(tunnel, checked)

ui/src/main/res/values/strings.xml

@@ -120,6 +120,7 @@
     <string name="error_down">Error bringing down tunnel: %s</string>
     <string name="error_fetching_apps">Error fetching apps list: %s</string>
     <string name="error_root">Please obtain root access and try again</string>
+    <string name="error_prepare">Error preparing tunnel: %s</string>
     <string name="error_up">Error bringing up tunnel: %s</string>
     <string name="exclude_private_ips">Exclude private IPs</string>
     <string name="generate_new_private_key">Generate new private key</string>