修复 当数据库一个数据都没有 BackupBbInSize 会出错

Project.SQLiteHelper/SQLiteHelper/SQLiteDbContext.cs

@@ -303,7 +303,8 @@ namespace SQLite
                 var firstTime = (DateTime)ret;
                 firstTimes.Add(firstTime);
             }
-
+            if (firstTimes.Count() == 0)
+                return;//no datas
 
             DateTime curr_month = new DateTime(DateTime.Now.Year, DateTime.Now.Month, 1);
             int curr_total_month = curr_month.Year * 12 + curr_month.Month;
@@ -451,7 +452,8 @@ namespace SQLite
             Regex regex = new Regex(@"\A(\d\d\d\d)-(\d\d)\z");
             var dirInfo = new DirectoryInfo(Path.GetDirectoryName(DBPath));
             var dirInfos = dirInfo.GetDirectories();
-
+            if (dirInfos == null || dirInfos.Count() == 0)
+                return;//什么都没有
             
             foreach (var dinfo in dirInfos) {
                 var match = regex.Match(dinfo.Name);