re PR tree-optimization/80079 (Conditional jump or move depends on uninitialised value(s): gimple-ssa-store-merging.c:768)

	PR tree-optimization/80079
	* gimple-ssa-store-merging.c (class pass_store_merging): Initialize
	m_stores_head.

Co-Authored-By: Markus Trippelsdorf <markus@trippelsdorf.de>

From-SVN: r246224