engine/function: catch thread errors in finalizer

It appears that the JavaScript context cannot be called from a finalizer.
For now, catch these errors.

Author: gi

lib/handlebars/engine/function.rb

@@ -16,7 +16,10 @@ def call(*args)
 
       def self.finalizer(context, name)
         proc {
-          context.eval("delete #{name}")
+          begin
+            context.eval("delete #{name}")
+          rescue ThreadError # rubocop:disable Lint/SuppressedException
+          end
         }
       end
     end