I didn't realize you had common anode bratan.
I was suggesting diodes for common cathode to prevent the max7219 from trying to source current into the cathode when it was put into shutdown mode.
Now that I think about it tho:
In common cathode, cathode goes to 7219 to prevent it from driving matrix cathodes high when in shutdown
In common anode, anode goes to 7219 to prevent it from pulling matrix anode low when in shutdown
In both cases, the non-driving 7219 is isolated from the common pin so the other part can control the shared line.
I'll draw this up when I get home.