Fix segfault in resolve_jobrules

In selectandinstall sometimes rules are added and a realloc is required if there's
no more memory available in the allocated block.  r-- would just decrement the old
pointer but the realloc could return a completely different block of memory

Author: tl-hbk

src/solver.c

@@ -1629,6 +1629,7 @@ resolve_jobrules(Solver *solv, int level, int disablerules, Queue *dq)
 	}
       olevel = level;
       level = selectandinstall(solv, level, dq, disablerules, i, SOLVER_REASON_RESOLVE_JOB);
+      r = solv->rules + i;    /* selectandinstall may have added more rules */
       if (level <= olevel)
 	{
 	  if (level == olevel)