add null guard around ammoUpdate

[gludington]

This null guard allows the hook to proceed even when calling the deprecated old hook, however, doing so reveals what appears to be a similar issue downstream in mixin.js, as on some subseuqent casts, in

_createDeprecatedConfigs(usageConfig, dialogConfig, messageConfig)

Uncaught (in promise) TypeError: usageConfig.consume?.resources.includes is not a function