Re-work error checking

services/filestore/app/coffee/ImageOptimiser.coffee

@@ -11,11 +11,12 @@ module.exports =
 			timeout: 30 * 1000
 			killSignal: "SIGKILL"
 		exec args, opts,(err, stdout, stderr)->
-			if err? and err?.signal == 'SIGKILL'
-				logger.warn {err: err, stderr: stderr, localPath: localPath}, "optimiser timeout reached"
-				err = null
 			if err?
-				logger.err err:err, stderr:stderr, localPath:localPath, "something went wrong converting compressPng"
+				if err.signal == 'SIGKILL'
+					logger.warn {err: err, stderr: stderr, localPath: localPath}, "optimiser timeout reached"
+					err = null
+				else
+					logger.err err:err, stderr:stderr, localPath:localPath, "something went wrong converting compressPng"
 			else
 				logger.log  localPath:localPath, "finished compressPng file"
 			callback(err)