[BUG] UI shows incorrect node state

[aresnow1]

Describe the bug

UI shows incorrect node state when two dataframes join.

To Reproduce

To help us reproducing this bug, please provide information below:

In [18]: df1 = md.read_csv('Downloads/ml-20m/movies.csv')

In [19]: df2 = md.read_csv('Downloads/ml-20m/ratings.csv')

In [20]: df1[['movieId', 'title']].merge(df2[['movieId', 'rating']], on="movieId").execute()

The UI shows,

Those nodes without color should be green.