尝试修复对单框架项目的支持

src/dotnetCampus.SourceYard/Context/MultiTargetingPackageInfo.cs

@@ -45,8 +45,9 @@ namespace dotnetCampus.SourceYard.Context
                     return true;
                 }
 
-                if (targetFrameworks != null)
+                if (targetFrameworks != null && string.IsNullOrWhiteSpace(targetFrameworks) is false)
                 {
+                    // 对于单框架，也许 targetFrameworks 的值是空字符串
                     if (targetFrameworks.Contains(t.TargetFramework) is false)
                     {
                         return true;

src/dotnetCampus.SourceYard/Program.cs

@@ -79,6 +79,8 @@ namespace dotnetCampus.SourceYard
 #endif
             var logger = new Logger();
 
+            FixOptions(options);
+
             try
             {
                 logger.Message("Source packaging");
@@ -179,6 +181,18 @@ namespace dotnetCampus.SourceYard
             }
         }
 
+        /// <summary>
+        /// 兼容修复
+        /// </summary>
+        /// <param name="options"></param>
+        private static void FixOptions(Options options)
+        {
+            if (string.IsNullOrWhiteSpace(options.MultiTargetingPackageInfoFolder))
+            {
+                options.MultiTargetingPackageInfoFolder = null!;
+            }
+        }
+
         /// <summary>
         /// 获取通用的 SourcePacking 文件夹，无视框架版本的不同
         /// </summary>
@@ -212,7 +226,7 @@ namespace dotnetCampus.SourceYard
             folder = Path.GetFullPath(folder);
             const string packageName = "Package";
 
-            if (string.IsNullOrEmpty(options.TargetFrameworks))
+            if (string.IsNullOrWhiteSpace(options.TargetFrameworks))
             {
                 // 单个框架的项目
                 var sourcePackingFolder = GetCommonSourcePackingFolder(multiTargetingPackageInfo, logger);