Fix random DocVector generation (shard cannot be negative)

Author: GalLalouche

x-pack/plugin/esql/compute/test/src/main/java/org/elasticsearch/compute/test/BlockTestUtils.java

@@ -38,6 +38,7 @@
 import static org.elasticsearch.test.ESTestCase.randomFloat;
 import static org.elasticsearch.test.ESTestCase.randomInt;
 import static org.elasticsearch.test.ESTestCase.randomLong;
+import static org.elasticsearch.test.ESTestCase.randomNonNegativeInt;
 import static org.elasticsearch.test.ESTestCase.randomRealisticUnicodeOfCodepointLengthBetween;
 import static org.hamcrest.Matchers.equalTo;
 import static org.junit.Assert.assertThat;
@@ -54,7 +55,7 @@ public static Object randomValue(ElementType e) {
             case DOUBLE -> randomDouble();
             case BYTES_REF -> new BytesRef(randomRealisticUnicodeOfCodepointLengthBetween(0, 5));   // TODO: also test spatial WKB
             case BOOLEAN -> randomBoolean();
-            case DOC -> new BlockUtils.Doc(randomInt(), randomInt(), between(0, Integer.MAX_VALUE));
+            case DOC -> new BlockUtils.Doc(randomNonNegativeInt(), randomInt(), between(0, Integer.MAX_VALUE));
             case NULL -> null;
             case COMPOSITE -> throw new IllegalArgumentException("can't make random values for composite");
             case AGGREGATE_METRIC_DOUBLE -> throw new IllegalArgumentException("can't make random values for aggregate_metric_double");