fix missing del command in post build

ignore of coreplugins is not working...

MediaBrowser.ServerApplication/MediaBrowser.ServerApplication.csproj

@@ -390,7 +390,7 @@ xcopy "$(TargetDir)x86" "$(SolutionDir)..\Deploy\Server\System\x86" /y
 mkdir "$(SolutionDir)..\Deploy\Server\System\CorePlugins"
 xcopy "$(TargetDir)CorePlugins" "$(SolutionDir)..\Deploy\Server\System\CorePlugins" /y
 
-del 
+del "$(SolutionDir)..\Deploy\MBServer.zip"
 "$(SolutionDir)7za" a -tzip "$(SolutionDir)..\Deploy\MBServer.zip" "$(SolutionDir)..\Deploy\Server\*"
 )</PostBuildEvent>
   </PropertyGroup>