Load(): Bug in some cases when loading a region and specifying a common grid.

As @nmishra reported, the following Load() call provides only NA values:

data <- Load('prlr', 'meteofrance/system4_m1', NULL, '19921101', output = 'lonlat', lonmin = -120, lonmax = 170, latmin = -70, latmax = 75, leadtimemin = 2, leadtimemax = 4, grid = 'r512x256')

Whereas the same call without the grid parameter provides the expected data.