Enable @typescript eslint/prefer nullish coalescing eslint rule (#1420)

## Description:

Fixes #952 
Enabled @typescript-eslint/prefer-nullish-coalescing rule and worked
through every error, introducing ?? and ??= operators or disabling
errors with inline comments where appropriate, to the best of my
ability.

## 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:

g_santos_m

src/client/graphics/layers/RadialMenuElements.ts

@@ -352,9 +352,9 @@ export const buildMenuElement: MenuElement = {
           : undefined,
         icon: item.icon,
         tooltipItems: [
-          { text: translateText(item.key || ""), className: "title" },
+          { text: translateText(item.key ?? ""), className: "title" },
           {
-            text: translateText(item.description || ""),
+            text: translateText(item.description ?? ""),
             className: "description",
           },
           {
@@ -401,7 +401,7 @@ export const boatMenuElement: MenuElement = {
 
     params.playerActionHandler.handleBoatAttack(
       params.myPlayer,
-      params.selected?.id() || null,
+      params.selected?.id() ?? null,
       params.tile,
       spawn !== false ? spawn : null,
     );