I tried many different solutions, but unfortunately with similar results to yours. Eventually, I found a solution for this problem. I hope it meets your needs.

1. Initialize variable (string)
2. After Search for users (V2) action add action "set variable" with dynamic content "Body" from Search for users (V2).
3. Then add condition where you compare your variable (is equal to) with this expression: string('{"value":[]}')

If the user has not been found, the “if yes” action will be performed. However, if the result of the condition is not true (i.e. information about the user was found) the “if no” action will be executed.