spark git commit: [SPARK-26198][SQL] Fix Metadata serialize null values throw NPE

Repository: spark Updated Branches: refs/heads/branch-2.3 0058986de -> 8236f6497 [SPARK-26198][SQL] Fix Metadata serialize null values throw NPE How to reproduce this issue: ```scala scala> val meta = new org.apache.spark.sql.types.MetadataBuilder().putNull("key").build().json

spark git commit: [SPARK-26198][SQL] Fix Metadata serialize null values throw NPE

Repository: spark Updated Branches: refs/heads/branch-2.4 58a4c0ce7 -> 91b86b7f3 [SPARK-26198][SQL] Fix Metadata serialize null values throw NPE ## What changes were proposed in this pull request? How to reproduce this issue: ```scala scala> val meta = new

spark git commit: [SPARK-26198][SQL] Fix Metadata serialize null values throw NPE

Repository: spark Updated Branches: refs/heads/master 9cda9a892 -> 676bbb244 [SPARK-26198][SQL] Fix Metadata serialize null values throw NPE ## What changes were proposed in this pull request? How to reproduce this issue: ```scala scala> val meta = new