Sum of numeric and "NA" values in NetLogo monitors

I have three types of agents: male, female, and hermaphrodite. All these agents have the attribute "weight".

During the simulation, there are periods when there are only male agents, other periods when there are only female agents, other periods when there are only hermaphrodite agents, and periods when all of them are present at the same time.

I would like to have a monitor in NetLogo that shows the average weight of male and female agents (no hermaphrodites), but when there is only one type of these agents (male or female) in the system, the monitor returns NA.

Is there a way to tell NetLogo to treat these NA as 0?

-----------------EDIT----------------

Thanks for the help Toby_Stoe! I tried your code but I think there is an issue in the procedure "to-report get-average-weight". It works perfect when there are only males or males + females, but when there are only females, it divided the weight / 2, and I don't know why because in your code clearly you are stating to divide / 2 when there are only males and females together. I put here the code related to the procedure "to-report get-average-weight" just in case I made a mistake in your code!

to-report get-average-weight
  let averageMaleWeight 0
  let averageFemaleWeight 0

  if maleCount > 0 [set averageMaleWeight totalMaleWeight / maleCount]
  
  if femaleCount > 0 [set averageFemaleWeight totalFemaleWeight / femaleCount]

  if maleCount > 0 and femaleCount > 0 [report (averageMaleWeight + averageFemaleWeight) / 2] 
  
  ifelse maleCount > 0 
  [report averageMaleWeight] 
  [ifelse femaleCount > 0 
    [report averageFemaleWeight] 
    [report 0]]
  end

globals [
  totalMaleWeight
  totalFemaleWeight
  maleCount
  femaleCount
]

to setup
  clear-all
  ; Your setup code goes here
  reset-counters
  reset-ticks
end

to reset-counters
  set totalMaleWeight 0
  set totalFemaleWeight 0
  set maleCount 0
  set femaleCount 0
end

to update-weights
  reset-counters
  ask turtles [
    if agent-type = "male" [
      set totalMaleWeight totalMaleWeight + weight
      set maleCount maleCount + 1
    ]
    if agent-type = "female" [
      set totalFemaleWeight totalFemaleWeight + weight
      set femaleCount femaleCount + 1
    ]
  ]
end

to-report get-average-weight
  let averageMaleWeight 0
  let averageFemaleWeight 0

  if maleCount > 0 [
    set averageMaleWeight totalMaleWeight / maleCount
  ]
  
  if femaleCount > 0 [
    set averageFemaleWeight totalFemaleWeight / femaleCount
  ]

  if maleCount > 0 and femaleCount > 0 [
    report (averageMaleWeight + averageFemaleWeight) / 2
  ] else if maleCount > 0 [
    report averageMaleWeight
  ] else if femaleCount > 0 [
    report averageFemaleWeight
  ] else [
    report 0
  ]
end

In this example, I've added a reset-counters procedure that resets the counters for male and female weights and counts. Then, in the update-weights procedure, the counters are updated based on the agents' attributes.

The get-average-weight reporter calculates the average weights based on the counters. If both male and female counts are greater than 0, it returns the average of both weights. If only the male count is greater than 0, it returns the average male weight. If only the female count is greater than 0, it returns the average female weight. Otherwise, if both counts are 0 (indicating no male or female agents), it returns 0.

By setting "0" as the default value in the last report statement, it will handle cases where there are no male or female agents and display 0 instead of "NA".