JS: fix NPE in incremental compilation

Fix NPE when compiling project incrementally and a file which
is not recompiled contains try/catch statement

js/js.translator/testData/box/incremental/catchScope.kt

@@ -0,0 +1,16 @@
+// FILE: a.kt
+
+inline fun baz(): String =
+        try {
+            "OK"
+        }
+        catch (e: Exception) {
+            "not OK"
+        }
+
+// FILE: b.kt
+// RECOMPILE
+
+fun box(): String {
+    return baz()
+}