Safe property access

Always use proper null safety patterns when accessing properties that might be null or undefined. This prevents runtime errors and improves code robustness.

Key practices:

1. Use optional chaining consistently at every level of nested property access: ```typescript // ❌ Inconsistent - still can cause runtime errors configResult.config?.selectedModelByRole.chat?.completionOptions

// ✅ Consistent optional chaining configResult.config?.selectedModelByRole?.chat?.completionOptions

2. Verify object type before accessing properties, especially with DOM elements:
```typescript
// ❌ Unsafe - activeElement could be null
document.activeElement.classList.contains("ProseMirror")

// ✅ Type-safe access
if (document.activeElement instanceof Element && 
    document.activeElement.classList.contains("ProseMirror"))

1. Use nullish coalescing to provide safe defaults: ```typescript // ❌ Unsafe - will throw if nodeTextValue is null/undefined startIndex = nodeTextValue.indexOf(query, startIndex);

// ✅ Safe with fallback startIndex = nodeTextValue?.indexOf(query, startIndex) ?? -1;

4. Prefer positive conditions for null checks:
```typescript
// ❌ Less readable
onTitleClick={!item.content ? undefined : handleTitleClick}

// ✅ More readable
onTitleClick={item.content ? handleTitleClick : undefined}