add dataset existence validation for uploadContentRequest

[myhau]

Problem

When creating load job that loads JSON from GCS emulator (https://github.com/fsouza/fake-gcs-server), BigQuery emulator fails with:

com.google.api.client.googleapis.json.GoogleJsonResponseException: 500 Internal Server Error POST http://localhost:33144/bigquery/v2/projects/test-project/jobs?prettyPrint=false {   "code" : 500,   "errors" : [ {     "location" : "",     "message" : "runtime error: invalid memory address or nil pointer dereference",     "reason" : "internalError",     "debugInfo" : ""   } ],   "message" : "runtime error: invalid memory address or nil pointer dereference" }

Solution

Check if dataset exists.

Possibly related

• fix: nilpointer when storing json data goccy/bigquery-emulator#189
• Node Client - load from file throwing error goccy/bigquery-emulator#136