Vectors.sqdist return inconsistent result for sparse/dense vectors when the vectors have different lengths

For two vectors of different lengths, Vectors.sqdist would return different result when the vectors are represented as sparse and dense respectively. Sample:
val s1 = new SparseVector(4, Array(0,1,2,3), Array(1.0, 2.0, 3.0, 4.0))
val s2 = new SparseVector(1, Array(0), Array(9.0))
val d1 = new DenseVector(Array(1.0, 2.0, 3.0, 4.0))
val d2 = new DenseVector(Array(9.0))
println(s1 == d1 && s2 == d2)
println(Vectors.sqdist(s1, s2))
println(Vectors.sqdist(d1, d2))
result:
true
93.0
64.0

More precisely, for the extra part, Vectors.sqdist would include it for sparse vectors and exclude it for dense vectors. I'll send a PR and we can have more detailed discussion there.