Additional null protection in the toString.

Author: piotrczarnas

dqops/src/main/java/com/dqops/execution/sensors/SensorExecutionRunParameters.java

@@ -592,7 +592,7 @@ public String toString() {
 
         // todo: more and better info
 
-        if (this.connection.getDuckdb() != null) {
+        if (this.connection != null && this.connection.getDuckdb() != null) {
             FileFormatSpec fileFormatSpec = FileFormatSpecProvider.resolveFileFormat(this.connection.getDuckdb(), this.table);
             if (fileFormatSpec != null) {
                 stringBuilder.append(", file format: ");