Aggregation query returns empty result when one of the label match dont have the data

I have a lot of series of metrics in the prometheus server.

example, metric1 {name=“test”} 10 , metric2{name=“ex”} 15 and metric2{name=“ex2”} 20…

when i do the promQL like below

sum by (name) sum_over_time(metric1{name=“test”}) + sum by (name) sum_over_time(metric2{name=“ex”})

It returns 25 as expected.

but when i do the query like
sum by (name) sum_over_time(metric1{name=“test”}) + sum by (name) sum_over_time(metric2{name=“notexists”})

It returns empty result instead of 10.

Please help on the correct query to achieve this. Is this an actual issue in the prometheus? Is it resolved or Are we tracking this by the PR or Bug id?.

Please help