COMMAND to work with optional data being not set. (microsoft#581)

Resp output format of COMMAND family of commands should continue to work even for commands that are registered with missing optional data.
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Co-authored-by: Badrish Chandramouli <[email protected]>

libs/server/Resp/RespCommandsInfo.cs

@@ -361,27 +361,37 @@ public static bool TryGetRespCommandInfo(RespCommand cmd,
         /// <returns>Serialized value</returns>
         public string ToRespFormat()
         {
-            var sb = new StringBuilder();
+            if (string.IsNullOrWhiteSpace(this.Name))
+                return "$-1\r\n";
 
+            var sb = new StringBuilder();
             sb.Append("*10\r\n");
             // 1) Name
             sb.Append($"${this.Name.Length}\r\n{this.Name}\r\n");
             // 2) Arity
             sb.Append($":{this.Arity}\r\n");
             // 3) Flags
-            sb.Append($"*{this.respFormatFlags.Length}\r\n");
-            foreach (var flag in this.respFormatFlags)
-                sb.Append($"+{flag}\r\n");
+            sb.Append($"*{this.respFormatFlags?.Length ?? 0}\r\n");
+            if (this.respFormatFlags != null && this.respFormatFlags.Length > 0)
+            {
+                foreach (var flag in this.respFormatFlags)
+                    sb.Append($"+{flag}\r\n");
+            }
+
             // 4) First key
             sb.Append($":{this.FirstKey}\r\n");
             // 5) Last key
             sb.Append($":{this.LastKey}\r\n");
             // 6) Step
             sb.Append($":{this.Step}\r\n");
             // 7) ACL categories
-            sb.Append($"*{this.respFormatAclCategories.Length}\r\n");
-            foreach (var aclCat in this.respFormatAclCategories)
-                sb.Append($"+@{aclCat}\r\n");
+            sb.Append($"*{this.respFormatAclCategories?.Length ?? 0}\r\n");
+            if (this.respFormatAclCategories != null && this.respFormatAclCategories.Length > 0)
+            {
+                foreach (var aclCat in this.respFormatAclCategories)
+                    sb.Append($"+@{aclCat}\r\n");
+            }
+
             // 8) Tips
             var tipCount = this.Tips?.Length ?? 0;
             sb.Append($"*{tipCount}\r\n");