Fix runtime error when chassis, motherboard and firmware are nil

[maveonair]

This pull request introduces changes to the remoteInfo function in the cmd/incus/info.go file. The changes primarily involve adding nil checks for the System struct's Chassis, Motherboard, and Firmware fields before attempting to print their details. This helps prevent potential nil pointer dereference errors and fixes #866.

Test output

❯ incus info --resources
System:
  Type: container

Load:
  Processes: 17
  Average: 0.04 0.20 0.27

CPU:
  Architecture: aarch64
  Caches:
    - Level 1 (type: Data): 0B
    - Level 1 (type: Instruction): 0B
    - Level 2 (type: Unified): 0B
  Cores:
    - Core 0
      Frequency: 2000Mhz
      Threads:
        - 0 (id: 0, online: true, NUMA node: 0)
    - Core 1
      Frequency: 2000Mhz
      Threads:
        - 0 (id: 1, online: true, NUMA node: 0)
    - Core 2
      Frequency: 2000Mhz
      Threads:
        - 0 (id: 2, online: true, NUMA node: 0)
    - Core 3
      Frequency: 2000Mhz
      Threads:
        - 0 (id: 3, online: true, NUMA node: 0)
    - Core 4
      Frequency: 2000Mhz
      Threads:
        - 0 (id: 4, online: true, NUMA node: 0)
    - Core 5
      Frequency: 2000Mhz
      Threads:
        - 0 (id: 5, online: true, NUMA node: 0)
    - Core 6
      Frequency: 2000Mhz
      Threads:
        - 0 (id: 6, online: true, NUMA node: 0)
    - Core 7
      Frequency: 2000Mhz
      Threads:
        - 0 (id: 7, online: true, NUMA node: 0)
    - Core 8
      Frequency: 2000Mhz
      Threads:
        - 0 (id: 8, online: true, NUMA node: 0)
    - Core 9
      Frequency: 2000Mhz
      Threads:
        - 0 (id: 9, online: true, NUMA node: 0)
  Frequency: 2000Mhz (min: 2000Mhz, max: 2000Mhz)

Memory:
  Free: 5.28GiB
  Used: 519.39MiB
  Total: 5.78GiB

NICs:
  Card 0:
    NUMA node: 0
    PCI address: 0000:00:01.0
    Driver: virtio-pci (6.7.11-orbstack-00143-ge6b82e26cd22)
  Card 1:
    NUMA node: 0
    PCI address: 0000:00:02.0
    Driver: virtio-pci (6.7.11-orbstack-00143-ge6b82e26cd22)
  Card 2:
    NUMA node: 0
    PCI address: 0000:00:03.0
    Driver: virtio-pci (6.7.11-orbstack-00143-ge6b82e26cd22)

Disks:
  Disk 0:
    NUMA node: 0
    ID: vda
    Device: 254:0
    Type: virtio
    Size: 389.74MiB
    Read-Only: true
    Removable: false
  Disk 1:
    NUMA node: 0
    ID: vdb
    Device: 254:16
    Type: virtio
    Size: 8.00TiB
    Read-Only: false
    Removable: false
    Partitions:
      - Partition 1
        ID: vdb1
        Device: 254:17
        Read-Only: false
        Size: 460.43GiB
  Disk 2:
    NUMA node: 0
    ID: vdc
    Device: 254:32
    Type: virtio
    Size: 7.00GiB
    Read-Only: false
    Removable: false
    Partitions:
      - Partition 1
        ID: vdc1
        Device: 254:33
        Read-Only: false
        Size: 4.00GiB
      - Partition 2
        ID: vdc2
        Device: 254:34
        Read-Only: false
        Size: 2.00GiB

PCI devices:
  Device 0:
    Address: 0000:00:00.0
    Vendor: 
    Vendor ID: 106b
    Product: 
    Product ID: 1a05
    NUMA node: 0
    IOMMU group: 0
    Driver: 
  Device 1:
    Address: 0000:00:01.0
    Vendor: 
    Vendor ID: 1af4
    Product: 
    Product ID: 1041
    NUMA node: 0
    IOMMU group: 0
    Driver: virtio-pci
  Device 2:
    Address: 0000:00:02.0
    Vendor: 
    Vendor ID: 1af4
    Product: 
    Product ID: 1041
    NUMA node: 0
    IOMMU group: 0
    Driver: virtio-pci
  Device 3:
    Address: 0000:00:03.0
    Vendor: 
    Vendor ID: 1af4
    Product: 
    Product ID: 1041
    NUMA node: 0
    IOMMU group: 0
    Driver: virtio-pci
  Device 4:
    Address: 0000:00:05.0
    Vendor: 
    Vendor ID: 1af4
    Product: 
    Product ID: 1043
    NUMA node: 0
    IOMMU group: 0
    Driver: virtio-pci
  Device 5:
    Address: 0000:00:06.0
    Vendor: 
    Vendor ID: 1af4
    Product: 
    Product ID: 1042
    NUMA node: 0
    IOMMU group: 0
    Driver: virtio-pci
  Device 6:
    Address: 0000:00:07.0
    Vendor: 
    Vendor ID: 1af4
    Product: 
    Product ID: 1042
    NUMA node: 0
    IOMMU group: 0
    Driver: virtio-pci
  Device 7:
    Address: 0000:00:08.0
    Vendor: 
    Vendor ID: 1af4
    Product: 
    Product ID: 1042
    NUMA node: 0
    IOMMU group: 0
    Driver: virtio-pci
  Device 8:
    Address: 0000:00:09.0
    Vendor: 
    Vendor ID: 1af4
    Product: 
    Product ID: 105a
    NUMA node: 0
    IOMMU group: 0
    Driver: virtio-pci
  Device 9:
    Address: 0000:00:0a.0
    Vendor: 
    Vendor ID: 1af4
    Product: 
    Product ID: 105a
    NUMA node: 0
    IOMMU group: 0
    Driver: virtio-pci
  Device 10:
    Address: 0000:00:0b.0
    Vendor: 
    Vendor ID: 1af4
    Product: 
    Product ID: 1044
    NUMA node: 0
    IOMMU group: 0
    Driver: virtio-pci

[stgraber]

Thanks!