Merge pull request #6275 from Expensify/chirag-logic-fix

Compare against null because sequenceNumber can be 0

src/libs/actions/Report.js

@@ -1197,7 +1197,9 @@ function updateLastReadActionID(reportID, sequenceNumber) {
 
     // Need to subtract 1 from sequenceNumber so that the "New" marker appears in the right spot (the last read
     // action). If 1 isn't subtracted then the "New" marker appears one row below the action (the first unread action)
-    const lastReadSequenceNumber = (sequenceNumber - 1) || reportMaxSequenceNumbers[reportID];
+    // Note: sequenceNumber can be 1 for the first message, so we can't use
+    // (sequenceNumber - 1) || reportMaxSequenceNumbers[reportID] because the first expression results in 0 which is falsy.
+    const lastReadSequenceNumber = _.isNumber(sequenceNumber) ? (sequenceNumber - 1) : reportMaxSequenceNumbers[reportID];
 
     // We call this method in many cases where there's nothing to update because we already updated it, so we avoid
     // doing an unnecessary server call if the last read is the same one we had already