Fix potential npe

Fix an unlikely npe, which can occur when replying to an asynchronous request.
A single instance of that has been reported to bugsense.
Use string references in string-arrays

This is good because the app could crash due to an incomplete translation.
Also it is easier to disable features which not fully implemented.
Merge commit '200e66829a6875f49126b4336185b09afa2a5991' into actionbar

* commit '200e66829a6875f49126b4336185b09afa2a5991':
  Use string references in string-arrays
  Fix potential npe

Conflicts:
	res/values-da/strings.xml
	res/values-nl/strings.xml
	res/values/strings.xml
	src/uk/org/ngo/squeezer/service/SqueezeService.java