Initialize before dereferencing

Always ensure buffers, containers, and data structures are properly initialized before passing them to functions that will dereference them. This prevents null pointer dereferences and undefined behavior.

Key practices:

1. Initialize buffers before use: When using dynamic containers like kvec, ensure they are properly sized before passing to functions that access their contents
2. Use null safety annotations: Apply FUNC_ATTR_NONNULL_ALL and similar attributes to function parameters that must not be null
3. Make precise assertions: Use specific assertions like assert(argc > 0) rather than assert(argc >= 0) when zero values are not valid
4. Handle potentially null returns: When calling functions like os_getenv() that can return null, check the result before dereferencing

Example from the codebase:

// Before: Potential null dereference
if (swap_exists_action != SEA_NONE) {
  choice = (sea_choice_T)do_dialog(VIM_WARNING, _("VIM - ATTENTION"), msg.items, ...);
}

// After: Ensure buffer is initialized
kv_resize(*msg, IOSIZE);  // Initialize buffer before use
if (swap_exists_action != SEA_NONE) {
  choice = (sea_choice_T)do_dialog(VIM_WARNING, _("VIM - ATTENTION"), msg.items, ...);
}

This approach prevents static analysis tools from flagging potential null dereferences and ensures runtime safety by establishing clear contracts about what data must be valid before use.