fix compilation of src/cljm/cljm failing in add-imps

this fixes a weird input case in `add-imps` that prevents src/cljm/cljm to compile

Exception in thread "main" java.lang.IllegalArgumentException: Don't know how to create ISeq from: clojure.lang.Symbol

```clojure
|| extend-type: HashMap; impls: (IPrintable (-pr-seq [coll opts] (let [pr-pair (fn [keyval] (pr-sequential pr-seq "" " " "" opts keyval))] (pr-sequential pr-pair "{" ", " "}" opts coll)))) >> impl-map:{IPrintable ((-pr-seq [coll opts] (let [pr-pair (fn [keyval] (pr-sequential pr-seq "" " " "" opts keyval))] (pr-sequential pr-pair "{" ", " "}" opts coll))))}
p: IPrintable f: -pr-seq  meths: ([coll opts] (let [pr-pair (fn [keyval] (pr-sequential pr-seq "" " " "" opts keyval))] (pr-sequential pr-pair "{" ", " "}" opts coll)))
```

I needed this to get DemoApp to work.