Minor graphical inconsistency

It isn't a problem per se, but a consequence of how the display grid and filter are "drawn" in relation to the total width of the panadapter in pixels.  There are several math functions used to calculate and draw the position of the grid lines based on the display zoom level which is related to the FFT bin width size.  At some combinations, there are going to be times where a drawn element does not fall on even pixel distances from center and since a pixel is an atomic display element, the result is a drawn display object may be off by a pixel.  Since the filter is symmetric around the carrier line,  I suspect the grid line is probably rounded up to a larger value by a pixel