Protect against i=0 degenerate plot

[gilmae]

Occasionally the Next Coordinate function picks points along the i=0 line to the left of the bulbs. This then results in a series of identical images as the generator continues to zoom into a more or less featureless area.

While this may be because the mandelbrot image generator is not giving enough resolution, mRandelbot itself should protect by rejecting any results of Next Coordinate that are -2 < r < -0.75, i=0

[gilmae]

You can see in the image it isn't completely featureless, but it is difficult to see and thus uninteresting.