Check for null keys in map? Presto

Question

I have a query that was running fine for a while now that was doing the following:

  MAP_AGG(key, value(which is a map))
      AS k_v1,
  MAP_CONCAT(
      k_v(some map),
      MAP_UNION_SUM(
          MAP(ARRAY[K], ARRAY[V])
      ) as k_v2

With some data from source that looks like this:

key	value	k_v	K	V
id_2	{"KEY2": "20"}	{"KEY4": "100"}	KEY8	100
id_1	{"KEY1": "96.25"}	{"KEY5": "150"}	KEY8	150

In which it provides a table as such:

k_v1	k_v2
{"id_2":{{"KEY2": "20"}, "id_1":{"KEY1": "96.25"}}	{{"KEY4": "100"}, {"KEY5": "150"}, {"KEY8": "250"}}

But now as a new job was running, I get an error stating that

"Failure": "map key cannot be null"

I'm trying to understand how to catch such a case with Presto, as it seems pretty verbose of a process to have to unnest these kinds of situations to check for null keys. Is there a more easier or built in solution to do this kind of check and remove that from the mapping?

Edit: I have hundred's of thousands of records that needs to be processed. The sample data above is to illustrate the schema.