Fail with a better error message when there are surprising null values in the output

Author: gab1one

org.knime.scijava.scripting.base/src/org/knime/scijava/scripting/base/CompileProductHelper.java

@@ -8,7 +8,7 @@
 
 /**
  * Interface for classes which wrap a compilation product. This may be a
- * CommandInfo (for Java scripts) or a ScriptInfo (basically everything else.
+ * CommandInfo (for Java scripts) or a ScriptInfo (everything else).
  *
  * @author Jonathan Hale
  */

org.knime.scijava.scripting.node/src/org/knime/scijava/scripting/node/SciJavaScriptingNodeModel.java

@@ -62,9 +62,10 @@
 import org.scijava.script.ScriptService;
 
 /**
- * NodeModel of the ScriptingNode
+ * NodeModel of the SciJava ScriptingNode.
  *
  * @author Jonathan Hale (University of Konstanz)
+ * @author Gabriel Einsdorf (University of Konstanz)
  */
 public class SciJavaScriptingNodeModel extends NodeModel {
 
@@ -411,6 +412,13 @@ public DataCell[] getCells(final DataRow row) {
 			}
 
 			final DataCell[] cells = m_outputrowService.getOutputDataCells();
+			for (DataCell cell : cells) {
+				if (cell == null) {
+					throw new IllegalStateException(
+							"Execution of script failed, please check the"
+							+ " syntax of your script and the log messages!");
+				}
+			}
 
 			m_compileProduct.resetModule(m_module);