How to select from one column or the other based on NULL values in R?

I am trying to set up an if else statement that allows me to create a third column based on information from two other columns. Here is a sample dataset.

df <- data.frame(RequestTimeSecs1 = c(0, 44, 65, "N/A", 100), RequestTimeSecs2 = c(0,46, 55, 77, 112))

I want to create a third column called "RequestTimeSecs" which takes values from ReqeustTimeSecs1 unless RequestTimeSecs1 has N/A values. In that case, I want to select from RequestTimeSecs2 column.

Here is what I have tried so far.

df$RequestTimeSecs <- ifelse((df$RequestTimeSecs1 != "N/A"), df$RequestTimeSecs1, df$RequestTimeSecs2)

When I do this, I am getting the following results

RequestTimeSecs1	RequestTimeSec2	RequestTimeSecs
0	0	1
44	46	3
65	55	4
N/A	77	77
100	112	2

So in RequestTimeSecs, I got the desired input for N/A value, it should be 77 however, I don't know where the rest of the row numbers are coming for. In RequestTimeSecs, I want the following numbers c(0,44,65,77,100).

Please let me know where I am messing up in setting up the if else statement