Fix Refresh function (#1526)

Author: LucGenetier

src/libraries/Microsoft.PowerFx.Core/Texl/Builtins/Refresh.cs

@@ -105,6 +105,11 @@ public override IEnumerable<Identifier> GetIdentifierOfModifiedValue(TexlNode[]
 
             identifierNode = null;
 
+            if (args.Length == 0)
+            {
+                return null;
+            }
+
             FirstNameNode firstNameNode = args[0]?.AsFirstName();
             identifierNode = firstNameNode;