* plug-ins/common/sparkle.c
	* plug-ins/common/spheredesigner.c
	* plug-ins/common/struc.c
	* plug-ins/common/tileit.c
	* plug-ins/common/warp.c
	* plug-ins/common/whirlpinch.c
	* plug-ins/common/wind.c: handle situation where intersection
	of selection and drawable is empty; progress on bug #155733.