AdConfig: Skip serialization if none

[pahearn73]

What

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Why

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How

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Test

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Checklist

• I have self-reviewed this PR
• I have added tests that prove the feature works or the fix is effective

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All committers have signed the CLA.

[github-actions]

Package	Line Rate	Health
device.thunder_ripple_sdk.src	15%	❌
distributor.general.src	2%	❌
core.main.src.processor	0%	❌
core.sdk.src.api.manifest	91%	✔
core.main.src	0%	❌
core.main.src.state	21%	❌
core.sdk.src.extn.ffi	80%	✔
core.main.src.utils	10%	❌
core.launcher.src.manager	7%	❌
core.main.src.service	31%	❌
core.sdk.src.extn	83%	✔
core.main.src.bootstrap	0%	❌
core.tdk.src.gateway	100%	✔
core.main.src.service.apps	47%	➖
core.launcher.src	0%	❌
core.tdk.src.utils	0%	❌
device.thunder.src	0%	❌
device.thunder_ripple_sdk.src.bootstrap	0%	❌
core.main.src.firebolt	1%	❌
core.main.src.service.extn	41%	❌
core.sdk.src.extn.client	91%	✔
device.thunder_ripple_sdk.src.processors.events	0%	❌
core.sdk.src.api	78%	✔
device.mock_device.src	52%	➖
core.main.src.firebolt.handlers	1%	❌
core.sdk.src.api.distributor	84%	✔
core.main.src.processor.storage	0%	❌
core.main.src.bootstrap.manifest	0%	❌
core.sdk.src.api.observability	68%	➖
device.thunder_ripple_sdk.src.client	74%	➖
core.sdk.src.utils	53%	➖
device.thunder.src.bootstrap	0%	❌
core.sdk.src.api.device	77%	✔
core.main.src.broker	23%	❌
core.sdk.src.api.firebolt	78%	✔
core.sdk.src.api.gateway	86%	✔
device.thunder_ripple_sdk.src.events	4%	❌
device.thunder_ripple_sdk.src.processors	10%	❌
core.sdk.src.framework	75%	➖
core.main.src.bootstrap.extn	0%	❌
openrpc_validator.src	90%	✔
core.main.src.state.cap	44%	➖
Summary	42% (16530 / 38991)	➖

Minimum allowed line rate is 41%