fix(validation): safely handle null values for *_subnets_per_az_count using can() (#231)

Author: nacholiya

variables.tf

@@ -517,7 +517,7 @@ variable "public_subnets_per_az_count" {
     EOT
   default     = null
   validation {
-    condition     = var.public_subnets_per_az_count == null || var.public_subnets_per_az_count > 0
+    condition     = var.public_subnets_per_az_count == null || try(var.public_subnets_per_az_count > 0, false)
     error_message = "The `public_subnets_per_az_count` value must be greater than 0 or null."
   }
 }
@@ -543,7 +543,7 @@ variable "private_subnets_per_az_count" {
     EOT
   default     = null
   validation {
-    condition     = var.private_subnets_per_az_count == null || var.private_subnets_per_az_count > 0
+    condition     = var.private_subnets_per_az_count == null || try(var.private_subnets_per_az_count > 0, false)
     error_message = "The `private_subnets_per_az_count` value must be greater than 0 or null."
   }
 }