Filter nil values defensively

Proactively filter out nil values from collections and validate non-empty states before processing to prevent runtime errors. This defensive approach prevents common issues like “Cannot read properties of null” errors and ensures robust data handling.

When working with collections that may contain nil values, filter them out before processing:

;; Before: Risk of null pointer errors
(let [blocks (util/sort-by-height blocks)]
  ...)

;; After: Safe processing
(let [blocks (util/sort-by-height (remove nil? blocks))]
  ...)

Use seq instead of seq? to check for non-empty collections:

;; Check if collection has content before processing
(when (seq paths)
  ;; Process paths safely
  ...)

While this pattern requires callers to handle nil states (leading to (remove nil?) throughout the codebase), it prevents more serious downstream errors and makes error handling explicit rather than allowing silent failures or confusing secondary errors.