Flash of incorrect theme in jQuery mode

[Jaifroid]

Similar to, but not exactly the same issue as #787, I notice this flashing particularly in jQuery mode. When in light theme, it flashes to dark between article loads, and when in dark theme, it flashes to light. This is not the case in SW mode. The fact that the flash is the opposite of the loaded theme implies it is not a hard-coded value, and should be fixable.