Canceling Create New Signal dialog creates (null) signal

[ian-cameron]

This is a minor thing when using the new Online Signal Configuration tool. The link to 'Create New Signal' will create a signal with the specified ID if you click OK in the popup dialog box. However, if you click Cancel in that dialog it will still create a signal, but with null ID.

[shanejohnson-atspm]

I merged this into the "cycles and plans" branch we have been working on.