Always provide safe defaults or fallbacks when working with optional or potentially undefined values. Avoid using non-null assertion operators (`!`) on optional parameters, and ensure proper handling in type checking and value merging scenarios. **Key practices:** - Use default objects instead of non-null assertions: `val(info || { props: {} })` instead of `val(info!)` - Order type checks to handle undefined cases first: check for object & not null, then boolean, then provide defaults - Provide fallbacks for missing values: `color: var(--ant-tooltip-color, ${tooltipColor})` instead of assuming the CSS variable exists - Skip undefined values in object merging to preserve existing values rather than overwriting with undefined **Example:** ```typescript // ❌ Dangerous - assumes info exists return val(info!) as T; // ✅ Safe - provides default return val(info || { props: {} as Props }) as T; // ❌ No fallback for missing CSS variable color: 'var(--ant-tooltip-color)', // ✅ Provides fallback color: `var(--ant-tooltip-color, ${tooltipColor})`, ``` This prevents runtime errors and ensures predictable behavior when dealing with optional or missing values.