This has now been fixed, and the fix will be rolled into Q2A 1.5.3. If you want to apply it now, make the following changes to qa-content/qa-ask.js:
1. In the first function qa_title_change() change:
qa_tag_hints();
... to...
qa_tag_hints(true);
2. Change the following line in function qa_tag_hints()
var parts=qa_tag_typed_parts(elem);
... to ...
var parts=skipcomplete ? null : qa_tag_typed_parts(elem);
3. And in the same function, change:
if (parts.typed && qa_tags_complete) {
... to ...
if (parts && parts.typed && qa_tags_complete) {
The final code in Q2A 1.5.3 will be a little different but it's the same idea.