QGIS python processing.runalg Clip returns None

I'm writing a script in pyQGIS, which would emulate measurement of a line by "walking" along it with a compass with constant length. I have a problem with the Clip algorythm from processing module, namely it returns None, regardless of whether I add layers as inputs or selected features. What do I do wrong? I believe, that should the clip result in an empty layer, it would still be there, just empty? Below is the piece of code with problems,

while d.measureLine(QgsPoint(coorFin[0],coorFin[1]),QgsPoint(coor[0],coor[1]))>step: # If the distance between current and last point is more than chosen step
    # Create buffer polygon around a point
    bufCirc = point.geometry().buffer(step,10) # do a buffer from existing point 

    buforek = QgsFeature()
    buforek.setGeometry(bufCirc)

# Create layer and put the polygon inside
    bufferLayer = QgsVectorLayer("Polygon", "temporary_polygons", "memory")
    pz = bufferLayer.dataProvider()
    bufferLayer.setCrs(my_crs)
    pz.addFeatures([buforek])
    bufferLayer.commitChanges()


# select the buffer
    buforSel = bufferLayer.setSelectedFeatures([buforek]) 

# Clip coastline with the buffer
    liniaWarstwa = processing.runandload("qgis:clip", selectedCoastLine, buforSel, "memory:liniaWarstwa")
    print liniaWarstwa
    layer = QgsMapLayerRegistry.instance().mapLayersByName("memory:liniaWarstwa")[0]

The print prints "none", QgsMapLayerRegistry says "index out of range".

Answer

In the newer versions of the Processing plugin, it would seem that you can no longer define the name of the output memory layer. The name of the algorithm is used instead (see similar post).

Therefore, you should replace the last section of your code with something similar:

# Clip coastline with the buffer
    processing.runandload("qgis:clip", selectedCoastLine, buforSel, None)
    layer = QgsMapLayerRegistry.instance().mapLayersByName("Clipped")[0]