Fix bug when a blog storage file doesn't exist.
Fix bug when a blog storage file doesn't exist.

skbkontur/NuGetGallery,mtian/SiteExtensionGallery,JetBrains/ReSharperGallery,mtian/SiteExtensionGallery,grenade/NuGetGallery_download-count-patch,grenade/NuGetGallery_download-count-patch,ScottShingler/NuGetGallery,projectkudu/SiteExtensionGallery,ScottShingler/NuGetGallery,KuduApps/NuGetGallery,KuduApps/NuGetGallery,JetBrains/ReSharperGallery,mtian/SiteExtensionGallery,ScottShingler/NuGetGallery,grenade/NuGetGallery_download-count-patch,skbkontur/NuGetGallery,projectkudu/SiteExtensionGallery,KuduApps/NuGetGallery,KuduApps/NuGetGallery,skbkontur/NuGetGallery,JetBrains/ReSharperGallery,projectkudu/SiteExtensionGallery,KuduApps/NuGetGallery