Fix nullability mismatch in deprecated newConfig extension (#122)

getCollectionConfigs() was tightened to take a non-null
BaseReplicatorConfiguration (CBL-7303), but the re-added 3.x
deprecated ReplicatorConfiguration?.newConfig extension still
passes its nullable receiver, breaking compilation.

Guard the call with this?.let { getCollectionConfigs(it) }. This
matches the 3.3 behavior: the ReplicatorConfiguration constructor
treats a null collection map as empty, so a null receiver yields
an empty configuration exactly as before.

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: borrrden

common/main/kotlin/com/couchbase/lite/ConfigurationFactories.kt

@@ -100,7 +100,7 @@ fun ReplicatorConfiguration?.newConfig(
     val endPt =
         target ?: this?.target ?: throw IllegalArgumentException("A ReplicatorConfiguration must specify an endpoint")
     val config = if (collections == null) {
-        ReplicatorConfiguration(endPt, getCollectionConfigs(this))
+        ReplicatorConfiguration(endPt, this?.let { getCollectionConfigs(it) })
     } else {
         val rc = ReplicatorConfiguration(endPt)
         // Lint will flip out if you try to use `forEach` here.