Fix cppcheck 2.15.0 warnings #7050

Job	Run time
classicmode_1d_3dgrid	4m 20s
classicmode_3d	8m 19s
kilonova_1d_1dgrid	4m 50s
kilonova_1d_3dgrid	4m 51s
kilonova_2d_2dgrid	6m 37s
kilonova_2d_2dgrid_barnesthermalisation	5m 42s
kilonova_2d_2dgrid_expansionopac	5m 5s
kilonova_2d_2dgrid_xcomgammaphotoion	5m 21s
kilonova_2d_3dgrid	7m 12s
nebular_1d_3dgrid	11m 19s
nebular_1d_3dgrid_limitbfest	13m 38s
classicmode_1d_3dgrid testmode ON	18m 6s
classicmode_3d testmode ON	24m 59s
kilonova_1d_1dgrid testmode ON	11m 18s
kilonova_1d_3dgrid testmode ON	13m 10s
kilonova_2d_2dgrid testmode ON	19m 57s
kilonova_2d_2dgrid_barnesthermalisation testmode ON	16m 46s
kilonova_2d_2dgrid_expansionopac testmode ON	14m 47s
kilonova_2d_2dgrid_xcomgammaphotoion testmode ON	15m 53s
kilonova_2d_3dgrid testmode ON	21m 16s
nebular_1d_3dgrid testmode ON	23m 56s
nebular_1d_3dgrid_limitbfest testmode ON	23m 47s
combine_checksums	16s
	4h 41m 25s

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