[DCP][state_dict] Remove the check of FSDP has root (#121544)

[mvpatel2000]

Cherry-pick for release branch

Root may not exist due to FSDP lazy initialization.

Pull Request resolved: #121544
Approved by: https://github.com/Skylion007
ghstack dependencies: #121273, #121276, #121290

Fixes #ISSUE_NUMBER

cc @mrshenli @pritamdamania87 @zhaojuanmao @satgera @gqchen @aazzolini @osalpekar @jiayisuse @H-Huang @kwen2501 @awgu @penguinwu @fegin @XilunWu @wanchaol @fduwjj @wz337 @tianyu-l @wconstab @yf225 @chauhang @d4l3k @LucasLLC

[pytorch-bot]

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✅ You can merge normally! (1 Unrelated Failure)

As of commit 2ffe8ca with merge base 86a2d67 ():

FLAKY - The following job failed but was likely due to flakiness present on trunk:

• pull / linux-focal-py3.12-clang10 / test (default, 1, 3, linux.2xlarge) (gh) (disabled by #123655 but the issue was closed recently and a rebase is needed to make it pass)
  test_binary_ufuncs.py::TestBinaryUfuncsCPU::test_logaddexp_cpu_complex128

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[wz337]

LGTM! Thanks for submitting