Some themes (Sea Spray, among others) are incomplete and do not define every element...

Some themes (Sea Spray, among others) are incomplete and do not define every element of the $color array as they probably should.  I moved the "last resort default theme" code up before the attempt to load the chosen theme to provide "sane" defaults should the theme be incomplete.

This is mainly an E_ALL fix.  The themes should be complete, IMO, but that's a job for another day.

** This may affect how things look depending on which theme you use.  If you notice a difference, it's because you were using an incomplete theme. **

git-svn-id: https://svn.code.sf.net/p/squirrelmail/code/trunk/squirrelmail@5466 7612ce4b-ef26-0410-bec9-ea0150e637f0