chore: fix encoder/decoder creation

[danisharora099]

Problem

With #1697, setting pubsub topic based on shardInfo was introduced.
a bug was spotted during property check where if the index is 0, it falls back to the DefaultPubsubTopic.

Solution

The PR removes the property check, and just checks the definition on pubsubTopicShardInfo

Another solution could be to add a specific unedefined check like: pubsubTopicShardInfo !== undefined but there are very little benefits of additional property checking on a type-safe system. (ref: #1697 (comment))

[github-actions]

size-limit report 📦

Path	Size	Loading time (3g)	Running time (snapdragon)	Total time
Waku core	78.36 KB (-0.01% 🔽)	1.6 s (-0.01% 🔽)	223 ms (+37.18% 🔺)	1.8 s
Waku Simple Light Node	240.88 KB (-0.01% 🔽)	4.9 s (-0.01% 🔽)	333 ms (+40.82% 🔺)	5.2 s
ECIES encryption	72.84 KB (-0.01% 🔽)	1.5 s (-0.01% 🔽)	226 ms (+86.38% 🔺)	1.7 s
Symmetric encryption	72.82 KB (-0.01% 🔽)	1.5 s (-0.01% 🔽)	298 ms (+96.64% 🔺)	1.8 s
DNS discovery	120.85 KB (0%)	2.5 s (0%)	328 ms (+116.73% 🔺)	2.8 s
Privacy preserving protocols	125.75 KB (0%)	2.6 s (0%)	218 ms (+31.31% 🔺)	2.8 s
Light protocols	75.93 KB (-0.01% 🔽)	1.6 s (-0.01% 🔽)	277 ms (+131.16% 🔺)	1.8 s
History retrieval protocols	74.85 KB (-0.01% 🔽)	1.5 s (-0.01% 🔽)	164 ms (+136.26% 🔺)	1.7 s
Deterministic Message Hashing	5.65 KB (0%)	113 ms (0%)	75 ms (+320.97% 🔺)	188 ms

[weboko]

Isn't it is fixed in #1740?

[danisharora099]

Isn't it is fixed in #1740?

#1740 is dependent on this PR. removed the commit fixing it there and this should be merged as a separate PR