Fix destroy on already destroyed scope

It seems that when trying to destroy a lot of markers (and their scopes) at once, sometimes an already destroyed scope would get destroyed again, which obviously doesn't work. Simply wrapping the call in an if statement should be enough to fix this error
Merge pull request #701 from gitnik/destroy-fix

Fix destroy attempt on already destroyed scope
Add support for templates without urls

Support loading of plain text templates with the url