Better error message when defining a datatype for BQRead

[hamnis]

Sometimes when defining a derived bqread instance we might define the data type incorrectly,
now we can get error messages like:

java.lang.NullPointerException: Cannot invoke "Object.getClass()" because "other" is null
	at no.nrk.bigquery.BQRead$$anon$2.read(BQRead.scala:120)
	at no.nrk.bigquery.BQRead$$anon$2.read(BQRead.scala:114)
	at no.nrk.bigquery.BQReadCompat.no$nrk$bigquery$BQReadCompat$$anon$1$$_$read$$anonfun$1(BQReadCompat.scala:38)
	at scala.collection.ArrayOps$.map$extension(ArrayOps.scala:932)
	at scala.IArray$package$IArray$.map(IArray.scala:179)
	at magnolia1.CaseClassDerivation$ProductCaseClass.construct(impl.scala:57)
	at no.nrk.bigquery.BQReadCompat$$anon$1.read(BQReadCompat.scala:40)
	at no.nrk.bigquery.BigQueryClient.synchronousQuery$$anonfun$1$$anonfun$1(BigQueryClient.scala:111)

The error is here that we get an optional value for the field, but our datatype has defined this as
String