[Bug Fix] Added null check for extracted aspect value

[rakhiagr]

Summary

Added null check for extracted aspect value.

For Graph queries, we are getting this Null Pointer Exception and analyzing the stack trace we found this could be a potential gap.

Error message:
NullPointerException: Cannot invoke "String.length()" because "content" is null,

Root cause:
java.lang.NullPointerException: Cannot invoke "String.length()" because "content" is null
	at com.fasterxml.jackson.core.JsonFactory.createParser(JsonFactory.java:1336)
	at com.linkedin.data.codec.JacksonDataCodec.stringToMap(JacksonDataCodec.java:136)
	at com.linkedin.metadata.dao.utils.RecordUtils.toRecordTemplate(RecordUtils.java:93)
	at com.linkedin.metadata.dao.EbeanLocalRelationshipQueryDAO.constructSnapshot(EbeanLocalRelationshipQueryDAO.java:377)
	at com.linkedin.metadata.dao.EbeanLocalRelationshipQueryDAO.lambda$findEntities$0(EbeanLocalRelationshipQueryDAO.java:106)

Testing Done

./gradlew build

Checklist

• The PR conforms to DataHub's Contributing Guideline (particularly Commit Message Format)
• Links to related issues (if applicable)
• Docs related to the changes have been added/updated (if applicable)

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 75.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 66.03%. Comparing base (489394c) to head (cbbab4f).

Files with missing lines	Patch %	Lines
...n/metadata/dao/EbeanLocalRelationshipQueryDAO.java	75.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #500      +/-   ##
============================================
- Coverage     66.05%   66.03%   -0.02%     
  Complexity     1547     1547              
============================================
  Files           137      137              
  Lines          6003     6004       +1     
  Branches        671      672       +1     
============================================
  Hits           3965     3965              
  Misses         1750     1750              
- Partials        288      289       +1     

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[jsdonn]

LGTM