Unable to Add Additional Extensible Attribute to infoblox_ip_allocation Resource with IPv6

[ppieprzycki]

When attempting to add an additional extensible attribute (ext_attr) to an existing infoblox_ip_allocation resource using an IPv6 CIDR, the operation results in a crash.

This issue only occurs when using an IPv6 address. When using IPv4, the issue is not present.

Steps to Reproduce:

1. Define the infoblox_ip_allocation resource with an initial ext_attr and an IPv6 address.

resource "infoblox_ip_allocation" "test_ip" {
  provider = infoblox.static
  ipv6_cidr = "2a00:1111:2222:3333:3::/80"
  fqdn  = "testip.testzone.io"
  enable_dns = false
  comment = "managed by tf"
  ext_attrs = jsonencode(
    {
        "ExtAttr1" = 10      
    }
  )
}

2. Apply the configuration with terraform apply and verify the resource.

3. Modify the ext_attrs by adding an additional attribute (e.g., ExtAttr2).

  ~ resource "infoblox_ip_allocation" "test_ip" {
      ~ ext_attrs           = jsonencode(
          ~ {
              + ExtAttr2    = 10
                # (1 unchanged element hidden)
            }
        )
        id                  = "..."
        # (10 unchanged attributes hidden)
    }

4. Attempt to apply the updated configuration.

Expected Behavior: Terraform should update the resource with the new extensible attribute without errors.

Actual Behavior: Terraform crashes with the following stack trace:

Stack trace from the terraform-provider-infoblox_v2.7.0 plugin:

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x2 addr=0x0 pc=0x1033396d4]

goroutine 65 [running]:
github.com/infobloxopen/terraform-provider-infoblox/infoblox.resourceAllocationUpdate(0x1400052cf00, {0x1035c1500?, 0x1400007c380})
        github.com/infobloxopen/terraform-provider-infoblox/infoblox/resource_infoblox_ip_allocation.go:497 +0x964
github.com/hashicorp/terraform-plugin-sdk/v2/helper/schema.(*Resource).update(0x10366f3e8?, {0x10366f3e8?, 0x14000373170?}, 0xd?, {0x1035c1500?, 0x1400007c380?})
        github.com/hashicorp/terraform-plugin-sdk/v2@v2.34.0/helper/schema/resource.go:828 +0x134
github.com/hashicorp/terraform-plugin-sdk/v2/helper/schema.(*Resource).Apply(0x14000111340, {0x10366f3e8, 0x14000373170}, 0x14000426c30, 0x1400052cd80, {0x1035c1500, 0x1400007c380})
        github.com/hashicorp/terraform-plugin-sdk/v2@v2.34.0/helper/schema/resource.go:947 +0x658
github.com/hashicorp/terraform-plugin-sdk/v2/helper/schema.(*GRPCProviderServer).ApplyResourceChange(0x14000328378, {0x10366f3e8?, 0x14000373080?}, 0x140005e25f0)
        github.com/hashicorp/terraform-plugin-sdk/v2@v2.34.0/helper/schema/grpc_provider.go:1153 +0xb08
github.com/hashicorp/terraform-plugin-go/tfprotov5/tf5server.(*server).ApplyResourceChange(0x14000235400, {0x10366f3e8?, 0x14000372630?}, 0x140001c6070)
        github.com/hashicorp/terraform-plugin-go@v0.23.0/tfprotov5/tf5server/server.go:865 +0x2b0
github.com/hashicorp/terraform-plugin-go/tfprotov5/internal/tfplugin5._Provider_ApplyResourceChange_Handler({0x103635e20?, 0x14000235400}, {0x10366f3e8, 0x14000372630}, 0x1400052c000, 0x0)
        github.com/hashicorp/terraform-plugin-go@v0.23.0/tfprotov5/internal/tfplugin5/tfplugin5_grpc.pb.go:518 +0x164
google.golang.org/grpc.(*Server).processUnaryRPC(0x14000144e00, {0x10366f3e8, 0x140003724e0}, {0x103673950, 0x1400023a300}, 0x14000000240, 0x140003279e0, 0x103b932f8, 0x0)
        google.golang.org/grpc@v1.64.0/server.go:1379 +0xba0
google.golang.org/grpc.(*Server).handleStream(0x14000144e00, {0x103673950, 0x1400023a300}, 0x14000000240)
        google.golang.org/grpc@v1.64.0/server.go:1790 +0xc80
google.golang.org/grpc.(*Server).serveStreams.func2.1()
        google.golang.org/grpc@v1.64.0/server.go:1029 +0x8c
created by google.golang.org/grpc.(*Server).serveStreams.func2 in goroutine 25
        google.golang.org/grpc@v1.64.0/server.go:1040 +0x150