fix(assets): safeguard against null InstrumentCategory during ETF/Fund scans

FinlyticAssets/Services/AssetsDbService.cs

@@ -221,8 +221,10 @@ public class AssetsDbService : IAssetsDbService
                     HasSubtypeChanges(existingEntity, dto))
                 {
                     existingEntity.Name = dto.Name;
-                    existingEntity.Type = dto.Type;
-                    existingEntity.InstrumentCategory = dto.InstrumentCategory;
+                    existingEntity.Type = dto.Type ?? existingEntity.Type ?? "stock";
+                    existingEntity.InstrumentCategory = !string.IsNullOrWhiteSpace(dto.InstrumentCategory) 
+                        ? dto.InstrumentCategory 
+                        : (existingEntity.InstrumentCategory ?? dto.Type ?? "stock");
                     existingEntity.HasCfd = dto.HasCfd;
                     existingEntity.LastUpdatedAt = now;
                     existingEntity.Tags = mappedTags;
@@ -242,6 +244,13 @@ public class AssetsDbService : IAssetsDbService
 
     private static AssetEntity MapDtoToEntity(TradeRepublicAsset dto)
     {
+        static string ResolveCategory(string? category, string? fallbackType, string defaultCategory)
+        {
+            if (!string.IsNullOrWhiteSpace(category)) return category;
+            if (!string.IsNullOrWhiteSpace(fallbackType)) return fallbackType;
+            return defaultCategory;
+        }
+
         return dto switch
         {
             TradeRepublicStock stock => new StockEntity
@@ -249,7 +258,7 @@ public class AssetsDbService : IAssetsDbService
                 Isin = stock.Isin,
                 Name = stock.Name,
                 Type = stock.Type,
-                InstrumentCategory = stock.InstrumentCategory,
+                InstrumentCategory = ResolveCategory(stock.InstrumentCategory, stock.Type, "stock"),
                 HasCfd = stock.HasCfd,
                 DerivativeProductCategories = stock.DerivativeProductCategories?.ToList() ?? new List<string>()
             },
@@ -258,7 +267,7 @@ public class AssetsDbService : IAssetsDbService
                 Isin = etf.Isin,
                 Name = etf.Name,
                 Type = etf.Type,
-                InstrumentCategory = etf.InstrumentCategory,
+                InstrumentCategory = ResolveCategory(etf.InstrumentCategory, etf.Type, "fund"),
                 HasCfd = etf.HasCfd,
                 DerivativeProductCategories = etf.DerivativeProductCategories?.ToList() ?? new List<string>()
             },
@@ -267,7 +276,7 @@ public class AssetsDbService : IAssetsDbService
                 Isin = syn.Isin,
                 Name = syn.Name,
                 Type = syn.Type,
-                InstrumentCategory = syn.InstrumentCategory,
+                InstrumentCategory = ResolveCategory(syn.InstrumentCategory, syn.Type, "synthetic"),
                 HasCfd = syn.HasCfd,
                 DerivativeProductCategories = syn.DerivativeProductCategories?.ToList() ?? new List<string>()
             },
@@ -276,7 +285,7 @@ public class AssetsDbService : IAssetsDbService
                 Isin = dto.Isin,
                 Name = dto.Name,
                 Type = dto.Type,
-                InstrumentCategory = dto.InstrumentCategory,
+                InstrumentCategory = ResolveCategory(dto.InstrumentCategory, dto.Type, "stock"),
                 HasCfd = dto.HasCfd
             }
         };