Remove usage of 'null' in favor of 'undefined'

frontend/src/wasm-communication/editor.ts

@@ -8,12 +8,12 @@ export type WasmEditorInstance = InstanceType<WasmRawInstance["JsEditorHandle"]>
 export type Editor = Readonly<ReturnType<typeof createEditor>>;
 
 // `wasmImport` starts uninitialized because its initialization needs to occur asynchronously, and thus needs to occur by manually calling and awaiting `initWasm()`
-let wasmImport: WasmRawInstance | null = null;
+let wasmImport: WasmRawInstance | undefined;
 
 // Should be called asynchronously before `createEditor()`
 export async function initWasm(): Promise<void> {
 	// Skip if the WASM module is already initialized
-	if (wasmImport !== null) return;
+	if (wasmImport !== undefined) return;
 
 	// Import the WASM module JS bindings and wrap them in the panic proxy
 	wasmImport = await import("@/../wasm/pkg").then(panicProxy);

frontend/src/wasm-communication/messages.ts

@@ -82,9 +82,9 @@ export type HintGroup = HintInfo[];
 export class HintInfo {
 	readonly keyGroups!: KeysGroup[];
 
-	readonly keyGroupsMac!: KeysGroup[] | null;
+	readonly keyGroupsMac!: KeysGroup[] | undefined;
 
-	readonly mouse!: MouseMotion | null;
+	readonly mouse!: MouseMotion | undefined;
 
 	readonly label!: string;
 
@@ -669,7 +669,7 @@ export type WidgetLayout = {
 
 export function defaultWidgetLayout(): WidgetLayout {
 	return {
-		layoutTarget: null,
+		layoutTarget: undefined,
 		layout: [],
 	};
 }