Prevent template renderer from rendering error (#14646)

When there is a panic during template rendering unrolled/render
will automatically render the error. This leads to the
panic being displayed in the page and not a 500 page

Fix #14467
Fix #14525

Signed-off-by: Andrew Thornton <art27@cantab.net>

modules/templates/base.go

@@ -92,5 +92,6 @@ func HTMLRenderer() *render.Render {
 		Asset:                     GetAsset,
 		AssetNames:                GetAssetNames,
 		IsDevelopment:             !setting.IsProd(),
+		DisableHTTPErrorRendering: true,
 	})
 }