Fixes error message.

Signed-off-by: Ralph Gasser <[email protected]>

vitrivr-engine-core/src/main/kotlin/org/vitrivr/engine/core/config/ingest/IngestionPipelineBuilder.kt

@@ -137,7 +137,7 @@ class IngestionPipelineBuilder(val config: IngestionConfig) {
             stages[it.key] = root
             for (operation in this.config.operations) {
                 if (!stages.containsKey(operation.key)) {
-                    stages[operation.key] = Operation(operation.key, operation.value.operator, config.operators[operation.value.operator] ?: throw IllegalArgumentException("Undefined operator '${it.value.operator}'"), operation.value.merge)
+                    stages[operation.key] = Operation(operation.key, operation.value.operator, config.operators[operation.value.operator] ?: throw IllegalArgumentException("Undefined operator '${operation.value.operator}'"), operation.value.merge)
                 }
                 for (inputKey in operation.value.inputs) {
                     if (!stages.containsKey(inputKey)) {