fix initialSequence undefined issue

Author: seveibar

src/components/SequenceAnnotator/index.js

@@ -11,11 +11,12 @@ import colors from "../../colors"
 
 export default function SequenceAnnotator(props: SequenceAnnotatorProps) {
   const [highlightedItems, changeHighlightedItems] = useState([])
-  const [sequence, changeSequence] = useState(
-    () =>
-      props.initialSequence.flatMap(entity =>
-        entity.label ? [entity] : stringToSequence(entity.text)
-      ) || stringToSequence(props.document)
+  const [sequence, changeSequence] = useState(() =>
+    props.initialSequence
+      ? props.initialSequence.flatMap(entity =>
+          entity.label ? [entity] : stringToSequence(entity.text)
+        )
+      : stringToSequence(props.document)
   )
   const colorLabelMap = useMemo(
     () =>