Components with no variables violate assertions

[cernoch]

Sometimes a component is generated, which contains no variables.

An assertion which detects these cases is given in 3c02806:

sharpSAT/include/sharpSAT/component_types/difference_packed_component.h

Lines 77 to 78 in 3c02806

	assert(rComp.varsBegin()->get<VariableIndex>() != varsSENTINEL
	&& "There are no variables in the component. That may be an issue.");

An examples test instance is given in 039a029:

sharpSAT/test/benchmark/mks/wiki_geometry.cnf

Lines 1 to 17 in 039a029

	p cnf 6 13
	c position 0 has variables 1..2
	c position 1 has variables 3..4
	c position 2 has variables 5..6
	2 1 0
	-2 -1 0
	4 3 0
	-4 -3 0
	6 5 0
	-6 -5 0
	-1 -6 0
	-4 -6 0
	3 0
	-5 -3 -1 0
	5 3 0
	5 1 0
	3 1 0

[cernoch]

A hot-fix has been given in branch bug-component-novars.

If someone fixes this properly, please send a proper fix to the same branch.