SI-7775 Exclude nulls when iterating sys props

The previous fix to deal with concurrent modification of system
properties doesn't handle null results introduced when a property
is removed.

This commit filters nulls for safety, and also adds a `names`
method to `sys.SystemProperties`.

The test is upgraded.

1 files changed, 3 insertions, 2 deletions

diff --git a/src/compiler/scala/tools/reflect/WrappedProperties.scala b/src/compiler/scala/tools/reflect/WrappedProperties.scala
index 523287fc66..348d000d15 100644
--- a/src/compiler/scala/tools/reflect/WrappedProperties.scala
+++ b/src/compiler/scala/tools/reflect/WrappedProperties.scala
@@ -30,9 +30,10 @@ trait WrappedProperties extends PropertiesTrait {
   def systemProperties: List[(String, String)] = {
     import scala.collection.JavaConverters._
     wrap {
+      // SI-7269,7775 Avoid `ConcurrentModificationException` and nulls if another thread modifies properties
       val props = System.getProperties
-      // SI-7269 Be careful to avoid `ConcurrentModificationException` if another thread modifies the properties map
-      props.stringPropertyNames().asScala.toList.map(k => (k, props.get(k).asInstanceOf[String]))
+      val it = props.stringPropertyNames().asScala.iterator map (k => (k, props getProperty k)) filter (_._2 ne null)
+      it.toList
     } getOrElse Nil
   }
 }