diff --git a/app/src/main/java/openfoodfacts/github/scrachx/openfood/models/entities/MapOfStringsToStringConverter.java b/app/src/main/java/openfoodfacts/github/scrachx/openfood/models/entities/MapOfStringsToStringConverter.java
index 3416feb852e8..8790c7a255c4 100644
--- a/app/src/main/java/openfoodfacts/github/scrachx/openfood/models/entities/MapOfStringsToStringConverter.java
+++ b/app/src/main/java/openfoodfacts/github/scrachx/openfood/models/entities/MapOfStringsToStringConverter.java
@@ -3,6 +3,8 @@
 import android.util.Base64;
 import android.util.Log;
 
+import androidx.annotation.NonNull;
+
 import org.greenrobot.greendao.converter.PropertyConverter;
 
 import java.io.ByteArrayInputStream;
@@ -13,42 +15,42 @@
 import java.util.HashMap;
 import java.util.Map;
 
+import static android.util.Base64.DEFAULT;
+
 class MapOfStringsToStringConverter implements PropertyConverter<Map<String, String>, String> {
     private static final String LOG_TAG;
 
     @Override
+    @NonNull
     public Map<String, String> convertToEntityProperty(String databaseValue) {
         if (databaseValue == null) {
-            return null;
+            return new HashMap<>();
         }
         try {
-            ByteArrayInputStream bis=new ByteArrayInputStream(Base64.decode(databaseValue,Base64.DEFAULT));
-            ObjectInputStream objectInputStream=new ObjectInputStream(bis);
+            ByteArrayInputStream bis = new ByteArrayInputStream(Base64.decode(databaseValue, DEFAULT));
+            ObjectInputStream objectInputStream = new ObjectInputStream(bis);
             objectInputStream.readObject();
-
-        } catch (IOException e) {
-            Log.e(LOG_TAG, "Cannot serialize map to database.", e);
-        } catch (ClassNotFoundException e) {
+        } catch (IOException | ClassNotFoundException e) {
             Log.e(LOG_TAG, "Cannot serialize map to database.", e);
         }
-        return null;
+        return new HashMap<>();
     }
 
     @Override
-    public String convertToDatabaseValue(Map<String, String> entityProperty) {
-        if (entityProperty == null) {
-            return null;
-        }
+    @NonNull
+    public String convertToDatabaseValue(Map<String, String> entity) {
+        HashMap<String, String> map = entity != null ? new HashMap<>(entity) : new HashMap<>();
+
         try {
-            ByteArrayOutputStream bos=new ByteArrayOutputStream();
-            ObjectOutputStream objectOutputStream=new ObjectOutputStream(bos);
-            objectOutputStream.writeObject(new HashMap<>(entityProperty));
+            ByteArrayOutputStream bos = new ByteArrayOutputStream();
+            ObjectOutputStream objectOutputStream = new ObjectOutputStream(bos);
+            objectOutputStream.writeObject(map);
             objectOutputStream.flush();
-            return Base64.encodeToString(bos.toByteArray(),Base64.DEFAULT);
+            return Base64.encodeToString(bos.toByteArray(), DEFAULT);
         } catch (IOException e) {
             Log.e(LOG_TAG, "Cannot serialize map to database.", e);
         }
-        return null;
+        return "";
     }
 
     static {
diff --git a/app/src/main/java/openfoodfacts/github/scrachx/openfood/models/entities/OfflineSavedProduct.java b/app/src/main/java/openfoodfacts/github/scrachx/openfood/models/entities/OfflineSavedProduct.java
index cefbf5393679..3ab6a4f0dd76 100644
--- a/app/src/main/java/openfoodfacts/github/scrachx/openfood/models/entities/OfflineSavedProduct.java
+++ b/app/src/main/java/openfoodfacts/github/scrachx/openfood/models/entities/OfflineSavedProduct.java
@@ -23,6 +23,7 @@
 @Entity
 public class OfflineSavedProduct implements Serializable {
     private static final long serialVersionUID = 1L;
+    @SuppressWarnings("NotNullFieldNotInitialized")
     @Index(unique = true)
     @NonNull
     private String barcode;
@@ -30,6 +31,7 @@ public class OfflineSavedProduct implements Serializable {
     private Long id;
     @Index
     private boolean isDataUploaded;
+    @SuppressWarnings("NotNullFieldNotInitialized")
     @NonNull
     @Convert(converter = MapOfStringsToStringConverter.class, columnType = String.class)
     private Map<String, String> productDetails;
@@ -70,16 +72,20 @@ public String getLanguage() {
 
     @Nullable
     public String getName() {
-        final Map<String, String> map = productDetails;
-        final String language = firstNotEmpty(map.get(ApiFields.Keys.LANG), "en");
-        return firstNotEmpty(map.get(ApiFields.Keys.lcProductNameKey(language)), map.get(ApiFields.Keys.lcProductNameKey("en")));
+        final String language = firstNotEmpty(productDetails.get(ApiFields.Keys.LANG), "en");
+        return firstNotEmpty(
+            productDetails.get(ApiFields.Keys.lcProductNameKey(language)),
+            productDetails.get(ApiFields.Keys.lcProductNameKey("en"))
+        );
     }
 
     @Nullable
     public String getIngredients() {
-        final Map<String, String> map = productDetails;
-        final String language = firstNotEmpty(map.get(ApiFields.Keys.LANG), "en");
-        return firstNotEmpty(map.get(ApiFields.Keys.lcIngredientsKey(language)), map.get(ApiFields.Keys.lcIngredientsKey("en")));
+        final String language = firstNotEmpty(productDetails.get(ApiFields.Keys.LANG), "en");
+        return firstNotEmpty(
+            productDetails.get(ApiFields.Keys.lcIngredientsKey(language)),
+            productDetails.get(ApiFields.Keys.lcIngredientsKey("en"))
+        );
     }
 
     @Nullable