Added missing default values to $name and $icon parameters.

post-to-slack.ps1

@@ -4,8 +4,8 @@
 param(
 	[string]$message='No message given',
 	[string]$channel,
-	[string]$name,
-	[string]$icon,
+	[string]$name='No name given',
+	[string]$icon='No icon given',
 	[Parameter(Mandatory=$true)][string]$webhook
 )