iter4_irgnm: check operator type
iter4_irgnm: check operator type

sdimoudi/bart,mrirecon/bart,sdimoudi/bart,sdimoudi/bart,sidward/bart,sidward/bart,sidward/bart,mrirecon/bart,mrirecon/bart,sidward/bart,mrirecon/bart,mrirecon/bart,sdimoudi/bart,sidward/bart,sdimoudi/bart