Only call isGooglePlayServiceAvailable if isPlayVersion is true

[atavism]

Fix for the following crash on desktop:

flutter: [2024-07-25 12:03:09.277149 | Catcher 2 | INFO] ---------- ERROR ----------
flutter: [2024-07-25 12:03:09.277174 | Catcher 2 | INFO] LateInitializationError: Field 'methodChannel' has not been initialized.
flutter: [2024-07-25 12:03:09.277197 | Catcher 2 | INFO]
flutter: [2024-07-25 12:03:09.277318 | Catcher 2 | INFO] ------- STACK TRACE -------
flutter: [2024-07-25 12:03:09.277430 | Catcher 2 | INFO] #0      Model.methodChannel (package:lantern/common/model.dart)
flutter: [2024-07-25 12:03:09.277454 | Catcher 2 | INFO] #1      SessionModel.isGooglePlayServiceAvailable (package:lantern/common/session_model.dart:855:26)
flutter: [2024-07-25 12:03:09.277475 | Catcher 2 | INFO] #2      _PlanCardState._processCheckOut (package:lantern/plans/plan_details.dart:166:54)
flutter: [2024-07-25 12:03:09.277494 | Catcher 2 | INFO] #3      _PlanCardState.onPlanTap (package:lantern/plans/plan_details.dart:142:11)
flutter: [2024-07-25 12:03:09.277512 | Catcher 2 | INFO] #4      _PlanCardState.build.<anonymous closure> (package:lantern/plans/plan_details.dart:30:22)
flutter: [2024-07-25 12:03:09.277531 | Catcher 2 | INFO] #5      CInkWell.build.<anonymous closure> (package:lantern/common/ui/custom/ink_well.dart:30:27)
flutter: [2024-07-25 12:03:09.277549 | Catcher 2 | INFO] #6      _InkResponseState.handleTap (package:flutter/src/material/ink_well.dart:1171:21)
flutter: [2024-07-25 12:03:09.277569 | Catcher 2 | INFO] #7      GestureRecognizer.invokeCallback (package:flutter/src/gestures/recognizer.dart:344:24)
flutter: [2024-07-25 12:03:09.277588 | Catcher 2 | INFO] #8      TapGestureRecognizer.handleTapUp (package:flutter/src/gestures/tap.dart:652:11)
flutter: [2024-07-25 12:03:09.277610 | Catcher 2 | INFO] #9      BaseTapGestureRecognizer._checkUp (package:flutter/src/gestures/tap.dart:309:5)
flutter: [2024-07-25 12:03:09.277631 | Catcher 2 | INFO] #10     BaseTapGestureRecognizer.handlePrimaryPointer (package:flutter/src/gestures/tap.dart:242:7)
flutter: [2024-07-25 12:03:09.277651 | Catcher 2 | INFO] #11     PrimaryPointerGestureRecognizer.handleEvent (package:flutter/src/gestures/recognizer.dart:696:9)
flutter: [2024-07-25 12:03:09.277671 | Catcher 2 | INFO] #12     PointerRouter._dispatch (package:flutter/src/gestures/pointer_router.dart:98:12)
flutter: [2024-07-25 12:03:09.277692 | Catcher 2 | INFO] #13     PointerRouter._dispatchEventToRoutes.<anonymous closure> (package:flutter/src/gestures/pointer_router.dart:143:9)
flutter: [2024-07-25 12:03:09.277710 | Catcher 2 | INFO] #14     _LinkedHashMapMixin.forEach (dart:collection-patch/compact_hash.dart:633:13)
flutter: [2024-07-25 12:03:09.277729 | Catcher 2 | INFO] #15     PointerRouter._dispatchEventToRoutes (package:flutter/src/gestures/pointer_router.dart:141:18)
flutter: [2024-07-25 12:03:09.277747 | Catcher 2 | INFO] #16     PointerRouter.route (package:flutter/src/gestures/pointer_router.dart:127:7)
flutter: [2024-07-25 12:03:09.277765 | Catcher 2 | INFO] #17     GestureBinding.handleEvent (package:flutter/src/gestures/binding.dart:495:19)
flutter: [2024-07-25 12:03:09.277783 | Catcher 2 | INFO] #18     GestureBinding.dispatchEvent (package:flutter/src/gestures/binding.dart:475:22)
flutter: [2024-07-25 12:03:09.277801 | Catcher 2 | INFO] #19     RendererBinding.dispatchEvent (package:flutter/src/rendering/binding.dart:425:11)
flutter: [2024-07-25 12:03:09.277819 | Catcher 2 | INFO] #20     GestureBinding._handlePointerEventImmediately (package:flutter/src/gestures/binding.dart:420:7)
flutter: [2024-07-25 12:03:09.277838 | Catcher 2 | INFO] #21     GestureBinding.handlePointerEvent (package:flutter/src/gestures/binding.dart:383:5)
flutter: [2024-07-25 12:03:09.277856 | Catcher 2 | INFO] #22     GestureBinding._flushPointerEventQueue (package:flutter/src/gestures/binding.dart:330:7)
flutter: [2024-07-25 12:03:09.277874 | Catcher 2 | INFO] #23     GestureBinding._handlePointerDataPacket (package:flutter/src/gestures/binding.dart:299:9)
flutter: [2024-07-25 12:03:09.277893 | Catcher 2 | INFO] #24     _invoke1 (dart:ui/hooks.dart:328:13)
flutter: [2024-07-25 12:03:09.277911 | Catcher 2 | INFO] #25     PlatformDispatcher._dispatchPointerDataPacket (dart:ui/platform_dispatcher.dart:442:7)
flutter: [2024-07-25 12:03:09.277929 | Catcher 2 | INFO] #26     _dispatchPointerDataPacket (dart:ui/hooks.dart:262:31)