Fix wrapped array hanlding wrt null by StdDeserializer (#4844)

Author: Stanislav Shcherbakov

src/main/java/com/fasterxml/jackson/databind/deser/std/StdDeserializer.java

@@ -360,6 +360,10 @@ protected T _deserializeWrappedValue(JsonParser p, DeserializationContext ctxt)
             T result = (T) handleNestedArrayForSingle(p, ctxt);
             return result;
         }
+        // 11-Dec-2024: [databind#4844] Caller needs to handle nulls before delegating
+        if (p.hasToken(JsonToken.VALUE_NULL)) {
+            return getNullValue(ctxt);
+        }
         return (T) deserialize(p, ctxt);
     }
 

src/test/java/com/fasterxml/jackson/databind/struct/UnwrapSingleArrayMiscTest.java

@@ -6,6 +6,8 @@
 
 import org.junit.jupiter.api.Test;
 
+import com.fasterxml.jackson.core.JsonFactory;
+import com.fasterxml.jackson.core.JsonParser;
 import com.fasterxml.jackson.core.type.TypeReference;
 import com.fasterxml.jackson.databind.*;
 import com.fasterxml.jackson.databind.exc.MismatchedInputException;
@@ -19,6 +21,10 @@ public class UnwrapSingleArrayMiscTest extends DatabindTestUtil
             .enable(DeserializationFeature.UNWRAP_SINGLE_VALUE_ARRAYS)
             .build();
 
+    static class StringWrapper {
+        public String value;
+    }
+
     /*
     /**********************************************************
     /* Tests methods, POJOs
@@ -78,4 +84,16 @@ public void testEnumMapUnwrapping() throws Exception
             verifyException(e, "more than one value");
         }
     }
+
+    // [databind#4844]: should work for wrapped null values too
+    @Test
+    public void testDeserializeArrayWithNullElement() throws Exception
+    {
+        StringWrapper v = UNWRAPPING_MAPPER
+            .readerFor(StringWrapper.class)
+            .readValue("{\"value\": [null]}");
+        
+        assertNotNull(v);
+        assertNull(v.value);
+    }
 }