Handle the case where stringContent is empty.

framework/src/Volo.Abp.Http.Client/Volo/Abp/Http/Client/DynamicProxying/DynamicHttpProxyInterceptor.cs

@@ -121,7 +121,12 @@ namespace Volo.Abp.Http.Client.DynamicProxying
                 return (T)(object)stringContent;
             }
 
-            return JsonSerializer.Deserialize<T>(await responseContent.ReadAsStringAsync());
+            if (stringContent.IsNullOrWhiteSpace())
+            {
+                return default;
+            }
+
+            return JsonSerializer.Deserialize<T>(stringContent);
         }
 
         private async Task<HttpContent> MakeRequestAsync(IAbpMethodInvocation invocation)