[SPARK-21418][SQL] NoSuchElementException: None.get in DataSourceScanExec with sun.io.serialization.extendedDebugInfo=true

## What changes were proposed in this pull request?

If no SparkConf is available to Utils.redact, simply don't redact.

## How was this patch tested?

Existing tests

Author: Sean Owen <sowen@cloudera.com>

Closes #19123 from srowen/SPARK-21418.

Author: srowen

core/src/main/scala/org/apache/spark/util/Utils.scala

@@ -2639,9 +2639,12 @@ private[spark] object Utils extends Logging {
    * Redact the sensitive information in the given string.
    */
   def redact(conf: SparkConf, text: String): String = {
-    if (text == null || text.isEmpty || !conf.contains(STRING_REDACTION_PATTERN)) return text
-    val regex = conf.get(STRING_REDACTION_PATTERN).get
-    regex.replaceAllIn(text, REDACTION_REPLACEMENT_TEXT)
+    if (text == null || text.isEmpty || conf == null || !conf.contains(STRING_REDACTION_PATTERN)) {
+      text
+    } else {
+      val regex = conf.get(STRING_REDACTION_PATTERN).get
+      regex.replaceAllIn(text, REDACTION_REPLACEMENT_TEXT)
+    }
   }
 
   private def redact(redactionPattern: Regex, kvs: Seq[(String, String)]): Seq[(String, String)] = {

sql/core/src/main/scala/org/apache/spark/sql/execution/DataSourceScanExec.scala

@@ -69,7 +69,7 @@ trait DataSourceScanExec extends LeafExecNode with CodegenSupport {
    * Shorthand for calling redactString() without specifying redacting rules
    */
   private def redact(text: String): String = {
-    Utils.redact(SparkSession.getActiveSession.get.sparkContext.conf, text)
+    Utils.redact(SparkSession.getActiveSession.map(_.sparkContext.conf).orNull, text)
   }
 }