Do not crash when nullable actions is null

[babbage]

Actions was made nullable in d93e351f4095d30a436fbf6ec3e3dc224e7905a1 but that same commit introduced a non-null assertion operator here which means it is valid to create a KeyboardActionsConfig with a null actions but this will crash KeyboardActions on init.

This PR ensures that a check is made if there are actions on the newConfig and only attempt to iterate over them when they exist. By assigning newConfig.actions to a local variable it is implicitly unwrapped once the null check has occurred.

The PR also removes the flutter_export_environment.sh file from the repo and adds it to the .gitignore file, as this file is not intended to be committed to source control.