unit upgrade minor improvements (#1337)

## Description:

forgot to push these changes to the branch before merging
513fcb0944

## 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
- [x] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced
- [x] I understand that submitting code with bugs that could have been
caught through manual testing blocks releases and new features for all
contributors

## Please put your Discord username so you can be contacted if a bug or
regression is found:

evan

src/client/graphics/layers/BuildMenu.ts

@@ -133,6 +133,9 @@ export class BuildMenu extends LitElement implements Layer {
 
   init() {
     this.eventBus.on(ShowBuildMenuEvent, (e) => {
+      if (!this.game.myPlayer()?.isAlive()) {
+        return;
+      }
       const clickedCell = this.transformHandler.screenToWorldCoordinates(
         e.x,
         e.y,
@@ -144,9 +147,6 @@ export class BuildMenu extends LitElement implements Layer {
         return;
       }
       const tile = this.game.ref(clickedCell.x, clickedCell.y);
-      if (!this.game.myPlayer()?.isAlive()) {
-        return;
-      }
       this.showMenu(tile);
     });
     this.eventBus.on(CloseViewEvent, () => this.hideMenu());
@@ -383,9 +383,6 @@ export class BuildMenu extends LitElement implements Layer {
   }
 
   public sendBuildOrUpgrade(buildableUnit: BuildableUnit, tile: TileRef): void {
-    if (buildableUnit === null) {
-      return;
-    }
     if (buildableUnit.canUpgrade !== false) {
       this.eventBus.emit(
         new SendUpgradeStructureIntentEvent(

src/core/game/PlayerImpl.ts

@@ -797,7 +797,7 @@ export class PlayerImpl implements Player {
   // Returns the existing unit that can be upgraded,
   // or false if it cannot be upgraded.
   // New units of the same type can upgrade existing units.
-  // e.g. if a place a new city here, will it upgrade an existing city?
+  // e.g. if a place a new city here, can it upgrade an existing city?
   private canUpgradeExistingUnit(
     type: UnitType,
     targetTile: TileRef,