run_migrations fails unless 2 arguments are specified

[znep]

The change in 713a57f to quote arguments broke running bin/run_migrations.sh without arguments since it now puts an "empty" invalid second arg in.

m@m:~/w/soda-fountain (master=)$ bin/run_migrations.sh
Using soda2.conf specified in /etc/soda2.conf environment variable
Running soda.server.MigrateSchema migrate ...
Exception in thread "main" java.lang.NumberFormatException: For input string: ""
at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
at java.lang.Integer.parseInt(Integer.java:504)
at java.lang.Integer.parseInt(Integer.java:527)
at scala.collection.immutable.StringLike$class.toInt(StringLike.scala:229)
at scala.collection.immutable.StringOps.toInt(StringOps.scala:31)
at com.socrata.soda.server.MigrateSchema$.main(MigrateSchema.scala:15)
at com.socrata.soda.server.MigrateSchema.main(MigrateSchema.scala)