feat: Posh.Host.UI.Box.TopWall ( Fixes #369 )

Only grabbing one character

Posh.types.ps1xml

@@ -1824,7 +1824,6 @@ $theseLines[0].Substring($theseLines[0].Length - 1)
     Gets a box's top wall character
 .DESCRIPTION
     Gets the top wall in a box.
-
 .NOTES
     If the box only has one line, and it is less than 5 characters, the second character will be considered the top wall.
 
@@ -1840,7 +1839,7 @@ if ($theLine.Length -lt 5) {
     # If there is only one line, it is between two and five characters    
     if ($theLine.Length -ge 2) {
         # pick the second character as the top wall
-        $theLine.Substring(1,2)
+        $theLine.Substring(1,1)
     } else {
         # (if there was only one character, it's the top wall)
         $theLine.Substring(0,1)
@@ -1849,12 +1848,6 @@ if ($theLine.Length -lt 5) {
     # Otherwise, pick one left of the middle in the line
     $theLine[[Math]::Floor($theLine.Length / 2) - 1]
 }
-
-
-
-
-
-
                     </GetScriptBlock>
       </ScriptProperty>
     </Members>