Wrong error message in VectorAssembler when column lengths can not be inferred

In VectorAssembler when input column lengths can not be inferred and handleInvalid = "keep", it will throw a runtime exception with message like below

Can not infer column lengths with handleInvalid = "keep". Consider using VectorSizeHint
|to add metadata for columns: [column1, column2]

However, even if you set vector size hint for column1, the message remains, and will not change to  [column2] only. This is not consistent with the description in the error message.

This introduce difficulties when I try to resolve this exception, for I do not know which column required vectorSizeHint. This is especially troublesome when you have a large number of columns to deal with.

Here is a simple example:

// create a df without vector size
val df = Seq(
  (Vectors.dense(1.0), Vectors.dense(2.0))
).toDF("n1", "n2")

// only set vector size hint for n1 column
val hintedDf = new VectorSizeHint()
  .setInputCol("n1")
  .setSize(1)
  .transform(df)

// assemble n1, n2
val output = new VectorAssembler()
  .setInputCols(Array("n1", "n2"))
  .setOutputCol("features")
  .setHandleInvalid("keep")
  .transform(hintedDf)

// because only n1 has vector size, the error message should tell us to set vector size for n2 too
output.show()

Expected error message:

Can not infer column lengths with handleInvalid = "keep". Consider using VectorSizeHint to add metadata for columns: [n2].

Actual error message:

Can not infer column lengths with handleInvalid = "keep". Consider using VectorSizeHint to add metadata for columns: [n1, n2].

I change one line in VectorAssembler.scala, so that it can work properly as expected.