Fixed some validation in the extension methods

The model obviously can't be casted to a string, so the check would always see the value as empty.

src/Skybrud.Umbraco.GridData/Extensions/TypedGridExtensionMethods.cs

@@ -89,9 +89,10 @@ public static HtmlString GetTypedGridHtml(this HtmlHelper html, GridDataModel mo
  /// <param name="property">The property holding the Grid model.</param>
  /// <param name="framework">The framework used to render the Grid.</param>
  public static HtmlString GetTypedGridHtml(this HtmlHelper html, IPublishedProperty property, string framework = DefaultFramework) {
-
- // Check whether the property value is empty
- if (String.IsNullOrWhiteSpace(property.Value as string)) return new HtmlString(String.Empty);
+
+ // Get the property value
+ GridDataModel value = property.Value as GridDataModel;
+ if (value == null) return new HtmlString(String.Empty);
 
  // Load the partial view based on the specified framework
  return html.Partial("TypedGrid/" + framework, property.Value);
@@ -130,8 +131,9 @@ public static HtmlString GetTypedGridHtml(this HtmlHelper html, IPublishedConten
  IPublishedProperty property = content.GetProperty(propertyAlias);
  if (property == null) throw new NullReferenceException("No property type found with alias " + propertyAlias);
 
- // Check whether the property value is empty
- if (String.IsNullOrEmpty(property.Value as string)) return new HtmlString(String.Empty);
+ // Get the property value
+ GridDataModel value = property.Value as GridDataModel;
+ if (value == null) return new HtmlString(String.Empty);
 
  // Load the partial view based on the specified framework
  return html.Partial("TypedGrid/" + framework, property.Value);
@@ -145,9 +147,10 @@ public static HtmlString GetTypedGridHtml(this HtmlHelper html, IPublishedConten
  /// <param name="html">The instance of <code>HtmlHelper</code>.</param>
  /// <param name="framework">The framework used to render the Grid.</param>
  public static HtmlString GetTypedGridHtml(this IPublishedProperty property, HtmlHelper html, string framework = DefaultFramework) {
-
- // Check whether the property value is empty
- if (String.IsNullOrEmpty(property.Value as string)) return new HtmlString(String.Empty);
+
+ // Get the property value
+ GridDataModel value = property.Value as GridDataModel;
+ if (value == null) return new HtmlString(String.Empty);
 
  // Load the partial view based on the specified framework
  return html.Partial("TypedGrid/" + framework, property.Value);
@@ -186,8 +189,9 @@ public static HtmlString GetTypedGridHtml(this IPublishedContent content, HtmlHe
  IPublishedProperty property = content.GetProperty(propertyAlias);
  if (property == null) throw new NullReferenceException("No property type found with alias " + propertyAlias);
 
- // Check whether the property value is empty
- if (String.IsNullOrEmpty(property.Value as string)) return new HtmlString(String.Empty);
+ // Get the property value
+ GridDataModel value = property.Value as GridDataModel;
+ if (value == null) return new HtmlString(String.Empty);
 
  // Load the partial view based on the specified framework
  return html.Partial("TypedGrid/" + framework, property.Value);