Fix variable's 'add to watch' feature. (#504)

* Fix variable's 'add to watch' feature.

Fix #838.

* Use results.Any() instead of .Count(), better perf.

Author: rkeithhill

src/PowerShellEditorServices.Protocol/DebugAdapter/Variable.cs

@@ -12,6 +12,11 @@ public class Variable
 		// /** The variable's value. For structured objects this can be a multi line text, e.g. for a function the body of a function. */
         public string Value { get; set; }
 
+        /// <summary>
+        /// Gets or sets the evaluatable name for the variable that will be evaluated by the debugger.
+        /// </summary>
+        public string EvaluateName { get; set; }
+
 		// /** If variablesReference is > 0, the variable is structured and its children can be retrieved by passing variablesReference to the VariablesRequest. */
         public int VariablesReference { get; set; }
 
@@ -21,6 +26,7 @@ public static Variable Create(VariableDetailsBase variable)
             {
                 Name = variable.Name,
                 Value = variable.ValueString ?? string.Empty,
+                EvaluateName = variable.Name,
                 VariablesReference = 
                     variable.IsExpandable ?
                         variable.Id : 0

src/PowerShellEditorServices/Debugging/DebugService.cs

@@ -603,7 +603,7 @@ await this.powerShellContext.ExecuteScriptString(
             // of command executions into string output.  However, if null is returned
             // then return null so that no output gets displayed.
             string outputString =
-                results != null ?
+                results != null && results.Any() ?
                     string.Join(Environment.NewLine, results) :
                     null;