[MNT-23094] Prevent ArrayIndexOutOfBoundsException when sorting by empty field

search-services/alfresco-search/src/main/java/org/alfresco/solr/AlfrescoCollatableTextFieldType.java

@@ -179,7 +179,14 @@ public class AlfrescoCollatableTextFieldType extends StrField
             else if (withLocale.startsWith("\u0000"))
             {
                 String[] parts = withLocale.split("\u0000");
-                return parts[2];
+                if (parts != null && parts.length == 3)
+                {
+                    return parts[2];
+                }
+                else
+                {
+                    return withLocale;
+                }
             }
             else
             {

search-services/alfresco-search/src/test/java/org/alfresco/solr/AlfrescoCollatableTextFieldTypeTest.java

@@ -173,4 +173,17 @@ public class AlfrescoCollatableTextFieldTypeTest
         verify(mockCollator).compare("NotNull1", "NotNull2");
         assertEquals("Expected result to be obtained from collator.", comparisonResult, result);
     }
+
+    @Test
+    public void testMNT23094()
+    {
+        // Set up the document to have an encoded value for the field.
+        when(mockDocTerms.get(DOC)).thenReturn(new BytesRef("\u0000"));
+        when(mockDocsWithField.get(DOC)).thenReturn(false);
+
+        // Call the method under test.
+        textSortFieldComparator.compareBottom(DOC);
+
+        verify(mockCollator).compare(BOTTOM_STRING, "\u0000");
+    }
 }