Fix: Prevent NPE in SpecRunHistory.sortFeatures when duration is missing (#2235)

This PR fixes a NullPointerException in SpecRunHistory.sortFeatures that
occurs when a .spock/RunHistory file contains a feature with a
confidence value but no recorded duration (e.g., due to an interrupted
or partially written test run).

Fixes #2234

Previously, Spock assumed all featureDurations entries were present and
performed direct unboxing to long, which fails when a value is null.

## Root cause
```
long duration1 = data.featureDurations.get(f1.getName());
long duration2 = data.featureDurations.get(f2.getName());
```

If either featureDurations.get(...) call returns null, the auto-unboxing
causes:

`Cannot invoke "java.lang.Long.longValue()" because the return value of
"java.util.Map.get(Object)" is null`


This typically happens when:

The previous run was aborted mid-write or during Gradle/IDE
synchronization.

The .spock/RunHistory file was created by a different version of Spock.

The file was partially deleted or corrupted manually.

## Fix

A small defensive check ensures safe comparison even if a duration is
missing:

```
Long d1 = data.featureDurations.get(f1.getName());
Long d2 = data.featureDurations.get(f2.getName());
if (d1 == null && d2 == null) return 0;
if (d1 == null) return 1;   // sort missing durations last
if (d2 == null) return -1;
return Long.compare(d1, d2);
```

This preserves existing behavior and avoids the NPE without changing
sort semantics or serialization.

---------

Co-authored-by: Andreas Turban <andreas.turban@net-baustelle.de>

Author: ThanosTsiamis

docs/release_notes.adoc

@@ -60,6 +60,7 @@ will now require that the spec is annotated with <<parallel_execution.adoc#isola
 * Fix vararg handling in SpyStatic spockIssue:2161[]
 * Fix incompatibility with JUnit 6 in OSGi environment spockIssue:2231[]
 * OSGi: Pin the `Require-Capability:osgi.ee=JavaSE` to Java `8` spockPull:2233[]
+* Fix: Prevent NPE in SpecRunHistory.sortFeatures when duration is missing spockIssue:2234[]
 
 == 2.4-M6 (2025-04-15)
 

spock-core/src/main/java/org/spockframework/runtime/SpecRunHistory.java

@@ -68,9 +68,12 @@ public void sortFeatures(SpecInfo spec) {
       if (!confidence1.equals(confidence2))
         return confidence1 - confidence2;
 
-      long duration1 = data.featureDurations.get(f1.getName()); // never null
-      long duration2 = data.featureDurations.get(f2.getName()); // never null
-      return duration1 < duration2 ? -1 : 1;
+      Long d1 = data.featureDurations.get(f1.getName());
+      Long d2 = data.featureDurations.get(f2.getName());
+
+      if (d1 == null) return 1;
+      if (d2 == null) return -1;
+      return d1< d2 ? -1 : 1;
     });
   }