Fixed fresh, careless bug in HighsMipSolverData::trivialHeuristics() #3556

Job	Run time
debug (ubuntu-latest)	4m 40s
debug64 (ubuntu-latest)	3m 34s
debug64_all_tests (ubuntu-latest)	4m 50s
debug_all_tests (ubuntu-latest)	4m 45s
release (ubuntu-latest)	3m 31s
release_all_tests (ubuntu-latest)	3m 36s
Release64_all_tests (ubuntu-latest)	3m 41s
Release64 (ubuntu-latest)	3m 22s
	31m 59s

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