Fix nullptr dereference segfault in QNN runtime when op_package_options is null

[RanjithRagavan]

This PR fixes a nullptr dereference segmentation fault in Qualcomm QNN backend's runtime when 'op_package_options' is not present in the serialized metadata (which is common for standard models). It adds null-safety checks before dereferencing options in QnnManager.cpp and QnnBackendCommon.cpp. Fixes #20619.

cc @cbilgin @psiddh

[pytorch-bot]

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❌ 2 New Failures, 2 Unrelated Failures

As of commit f4068e0 with merge base b1ef9a5 ():

NEW FAILURES - The following jobs have failed:

• pull / unittest / linux / linux-job (gh)
  RuntimeError: Command docker exec -t 9b1f2e0ce358c7b91d8cf4529486a05eb8ab9a85a29ec2e6a5152de92d92319e /exec failed with exit code 1
• pull / unittest-editable / linux / linux-job (gh)
  RuntimeError: Command docker exec -t c0d08697bf6b41b56172c66d09319317aec0c31ba880d68228f983803e0bf2d0 /exec failed with exit code 1

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

• pull / test-qnn-testsuite-linux / test-backend-linux (qnn, models) / linux-job (gh) (detected as infra flaky with no log or failing log classifier)

BROKEN TRUNK - The following job failed but was present on the merge base:

👉 Rebase onto the `viable/strict` branch to avoid these failures

• pull / unittest-nxp-neutron / linux-job (gh) (trunk failure)
  ##[error]The operation was canceled.

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[RanjithRagavan]

@pytorchbot label "release notes: none"

[shewu-quic]

LGTM. Thanks for your fix