Debounce.flush not invoked if lastArgs not defined

Editor assessment

The subject is a model of precision: debounce.flush was not invoked when lastArgs was undefined, naming the function, the condition, and the symptom in one line. The fix type is exactly right, and the absent scope is fine for a single utility. No body is present, which is acceptable for a narrowly scoped bug whose trigger condition the subject fully states, though a line on the guard added would have been welcome. The PR reference is well-formed. Imperative mood, no period, compact length. A crisp, self-sufficient bugfix message.