startRow in getLocalContext now falls back to undefined

Author: aviatesk

lib/misc/blocks.js

@@ -130,7 +130,7 @@ export function get (ed) {
 export function getLocalContext (editor, row) {
   const range = getRange(editor, row)
   const context = range ? editor.getTextInBufferRange(range) : ''
-  const startRow = range ? range[0][0] : null
+  const startRow = range ? range[0][0] : undefined
   return {
     context,
     startRow