[JENKINS-39495] Defend against a null serialized ParametersAction.par…

…ameters.

(cherry picked from commit ff34532)

core/src/main/java/hudson/model/ParametersAction.java

@@ -87,7 +87,7 @@ public class ParametersAction implements RunAction2, Iterable<ParameterValue>, Q
 
     private Set<String> safeParameters;
 
-    private final List<ParameterValue> parameters;
+    private @Nonnull List<ParameterValue> parameters;
 
     private List<String> parameterDefinitionNames;
 
@@ -99,7 +99,7 @@ public class ParametersAction implements RunAction2, Iterable<ParameterValue>, Q
 
     private transient Run<?, ?> run;
 
-    public ParametersAction(List<ParameterValue> parameters) {
+    public ParametersAction(@Nonnull List<ParameterValue> parameters) {
         this.parameters = new ArrayList<>(parameters);
         String paramNames = SystemProperties.getString(SAFE_PARAMETERS_SYSTEM_PROPERTY_NAME);
         safeParameters = new TreeSet<>();
@@ -284,6 +284,9 @@ public ParametersAction merge(@CheckForNull ParametersAction overrides) {
     }
 
     private Object readResolve() {
+        if (parameters == null) { // JENKINS-39495
+            parameters = Collections.emptyList();
+        }
         if (build != null)
             OldDataMonitor.report(build, "1.283");
         if (safeParameters == null) {