According to the lyrics of one of Irving Berlin’s most famous tunes, love and the weather can’t be depended upon – they’re unpredictable, irresponsible, unbelievable, unreliable. The same adjectives can’t be lobbed at “White Christmas,” which is one of those musical chestnuts that’s always going to work no matter how unapologetically cornball and old-fashioned it might be. Featuring more than a dozen of the legendary songwriter’s signature melodies, it’ll likely put you in the yuletide spirit, even if you know where the plot is heading from the first scene. The Spokane Civic Theatre’s latest production of “White Christmas” – it previously staged the show in 2010 and 2012 – has the worn-in feel of a veteran theatrical company dusting off one of its most treasured shows for the thousandth time. In fact, its stars, Kevin Partridge and Mark Pleasant, have both played their respective roles before in earlier productions, and their obvious ease when handling this material is part of its charm.