Fix the default color for the top bar text.
Fix the default color for the top bar text.

My change to improve the color capabilities for the page themes had
temporarily had a default color of white. Unfortunately, I committed
this. This fixes it and turns it back into black.

davidt/reviewboard,chipx86/reviewboard,davidt/reviewboard,reviewboard/reviewboard,chipx86/reviewboard,brennie/reviewboard,brennie/reviewboard,reviewboard/reviewboard,brennie/reviewboard,reviewboard/reviewboard,chipx86/reviewboard,sgallagher/reviewboard,brennie/reviewboard,davidt/reviewboard,chipx86/reviewboard,sgallagher/reviewboard,reviewboard/reviewboard,sgallagher/reviewboard,davidt/reviewboard,sgallagher/reviewboard