处理 非正常 Provider GC 可能为 null 的错误

Providers/FreeSql.Provider.MySql/MySqlProvider.cs

@@ -71,7 +71,7 @@ namespace FreeSql.MySql {
 		bool _isdisposed = false;
 		public void Dispose() {
 			if (_isdisposed) return;
-			(this.Ado as AdoProvider).Dispose();
+			(this.Ado as AdoProvider)?.Dispose();
 		}
 	}
 }

Providers/FreeSql.Provider.Oracle/OracleProvider.cs

@@ -48,7 +48,7 @@ namespace FreeSql.Oracle {
 		bool _isdisposed = false;
 		public void Dispose() {
 			if (_isdisposed) return;
-			(this.Ado as AdoProvider).Dispose();
+			(this.Ado as AdoProvider)?.Dispose();
 		}
 	}
 }

Providers/FreeSql.Provider.PostgreSQL/PostgreSQLProvider.cs

@@ -98,7 +98,7 @@ namespace FreeSql.PostgreSQL {
 		bool _isdisposed = false;
 		public void Dispose() {
 			if (_isdisposed) return;
-			(this.Ado as AdoProvider).Dispose();
+			(this.Ado as AdoProvider)?.Dispose();
 		}
 	}
 }

Providers/FreeSql.Provider.SqlServer/SqlServerProvider.cs

@@ -55,7 +55,7 @@ namespace FreeSql.SqlServer {
 		bool _isdisposed = false;
 		public void Dispose() {
 			if (_isdisposed) return;
-			(this.Ado as AdoProvider).Dispose();
+			(this.Ado as AdoProvider)?.Dispose();
 		}
 	}
 }

Providers/FreeSql.Provider.Sqlite/SqliteProvider.cs

@@ -47,7 +47,7 @@ namespace FreeSql.Sqlite {
 		bool _isdisposed = false;
 		public void Dispose() {
 			if (_isdisposed) return;
-			(this.Ado as AdoProvider).Dispose();
+			(this.Ado as AdoProvider)?.Dispose();
 		}
 	}
 }