Fix panic when ng.LaunchTemplate is nil

[july2993]

Description of your changes

When LaunchTemplate is nil at aws, but not nil at resource, this will panic.

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x10 pc=0x3662412]

goroutine 5134 [running]:
github.com/crossplane-contrib/provider-aws/pkg/clients/eks.LateInitializeNodeGroup(0xc03cb6d2c8, 0xc031b40fc0)
        github.com/crossplane-contrib/provider-aws/pkg/clients/eks/nodegroup.go:287 +0x432
github.com/crossplane-contrib/provider-aws/pkg/controller/eks/nodegroup.(*external).Observe(0xc03da49780, {0x6a47570, 0xc0418b7620}, {0x6a7ce58?, 0xc03cb6d180})
        github.com/crossplane-contrib/provider-aws/pkg/controller/eks/nodegroup/controller.go:114 +0x207
github.com/crossplane/crossplane-runtime/pkg/reconciler/managed.(*Reconciler).Reconcile(0xc000642bb0, {0x6a475a8, 0xc036f3c2d0}, {{{0x0?, 0x5e3ab60?}, {0xc005922740?, 0x30?}}})
        github.com/crossplane/crossplane-runtime@v0.19.0-rc.0.0.20220930073209-84e629b95898/pkg/reconciler/managed/reconciler.go:780 +0x287f
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).Reconcile(0xc000642c60, {0x6a475a8, 0xc036f3c210}, {{{0x0?, 0x5e3ab60?}, {0xc005922740?, 0x4041f4?}}})
        sigs.k8s.io/controller-runtime@v0.11.0/pkg/internal/controller/controller.go:114 +0x27e
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).reconcileHandler(0xc000642c60, {0x6a47500, 0xc000b40080}, {0x5911420?, 0xc005d5a740?})
        sigs.k8s.io/controller-runtime@v0.11.0/pkg/internal/controller/controller.go:311 +0x349
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).processNextWorkItem(0xc000642c60, {0x6a47500, 0xc000b40080})
        sigs.k8s.io/controller-runtime@v0.11.0/pkg/internal/controller/controller.go:266 +0x1d9
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).Start.func2.2()
        sigs.k8s.io/controller-runtime@v0.11.0/pkg/internal/controller/controller.go:227 +0x85
created by sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).Start.func2
        sigs.k8s.io/controller-runtime@v0.11.0/pkg/internal/controller/controller.go:223 +0x31c

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How has this code been tested