1. fixed DataSourceFilter error

Author: Ahoo-Wang

src/SmartSql/DataSourceFilter.cs

@@ -42,6 +42,7 @@ private IDataSource GetDataSource(DataSourceChoice sourceChoice)
             IDataSource choiceDataSource = _smartSqlContext.Database.WriteDataSource;
             var readDataSources = _smartSqlContext.Database.ReadDataSources;
             if (sourceChoice == DataSourceChoice.Read
+                && readDataSources != null
                 && readDataSources.Count > 0
                 )
             {

src/SmartSql/SmartSql.csproj

@@ -11,10 +11,10 @@
     <PackageProjectUrl>https://github.com/Ahoo-Wang/SmartSql</PackageProjectUrl>
     <RepositoryUrl>https://github.com/Ahoo-Wang/SmartSql</RepositoryUrl>
     <PackageRequireLicenseAcceptance>False</PackageRequireLicenseAcceptance>
-    <Version>3.5.12</Version>
+    <Version>3.5.13</Version>
     <PackageTags>orm sql read-write-separation cache  redis dotnet-core cross-platform high-performance distributed-computing zookeeper</PackageTags>
     <PackageReleaseNotes>
-      1. fixed Tag.For NotDirectValue bug
+      1. fixed DataSourceFilter error
     </PackageReleaseNotes>
     <PackageIconUrl>https://raw.githubusercontent.com/Ahoo-Wang/SmartSql/master/SmartSql.png</PackageIconUrl>
     <PackageLicenseUrl>https://raw.githubusercontent.com/Ahoo-Wang/SmartSql/master/LICENSE</PackageLicenseUrl>