Validate spawn tile (#1512)

## Description:

Enforce valid tile during spawn, to prevent the game from crashing for
all players.

## Please complete the following:

- [x] I have added screenshots for all UI updates
- [x] I process any text displayed to the user through translateText()
and I've added it to the en.json file
- [x] I have added relevant tests to the test directory
- [ ] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced
- [ ] I have read and accepted the CLA aggreement (only required once).

src/client/graphics/layers/PlayerActionHandler.ts

@@ -1,5 +1,5 @@
 import { EventBus } from "../../../core/EventBus";
-import { Cell, PlayerActions, PlayerID } from "../../../core/game/Game";
+import { PlayerActions, PlayerID } from "../../../core/game/Game";
 import { TileRef } from "../../../core/game/GameMap";
 import { PlayerView } from "../../../core/game/GameView";
 import {
@@ -61,8 +61,9 @@ export class PlayerActionHandler {
   ): Promise<TileRef | false> {
     return await player.bestTransportShipSpawn(tile);
   }
-  handleSpawn(spawnCell: Cell) {
-    this.eventBus.emit(new SendSpawnIntentEvent(spawnCell));
+
+  handleSpawn(tile: TileRef) {
+    this.eventBus.emit(new SendSpawnIntentEvent(tile));
   }
 
   handleAllianceRequest(player: PlayerView, recipient: PlayerView) {