prevent null dereferences

Always verify pointers are valid before dereferencing to prevent crashes and undefined behavior. This applies to regular pointers, weak pointers, and return values from C functions that may return null.

Use implicit bool conversion instead of explicit null comparisons for cleaner code:

// Preferred
if (ptr) {
    ptr->doSomething();
}

// Avoid
if (ptr != nullptr) {
    ptr->doSomething();
}

For weak pointers, use the appropriate check method:

• Use operator bool or .expired() when you only need to test validity
• Use .lock() only when you need the actual shared pointer

Apply guard patterns with early returns to reduce nesting:

if (!ptr)
    return;
    
ptr->doSomething();

Pay special attention to C function returns that may be null:

const char* env = getenv("VAR_NAME");
if (!env)
    return defaultValue;

Critical areas requiring null checks include: pointer dereferences in event handlers, accessing monitor/window objects that may be destroyed, and any pointer obtained from external APIs or lookups.