Interval is set to 0 the first time settings is accessed

[Mikko Ahlroth]

If the localstorage hasn't been used yet, there are no initial values for settings so they return null, which is converted to 0 on the slider. Default values should be added.

[Mikko Ahlroth]

Use default value for localstorage read when no stored value, fixes #1

→ <<cset 9e8d35ea2bd9>>