Fix PMD warnings.

Author: uhafner

Jenkinsfile

@@ -1,5 +1,8 @@
 def configurations = [
-  [ platform: "linux", jdk: "11" ]
+  [ platform: "linux", jdk: "11" ],
+  [ platform: "windows", jdk: "11" ]
 ]
 
-buildPlugin(failFast: false, configurations: configurations)
+buildPlugin(failFast: false, configurations: configurations,
+    checkstyle: [qualityGates: [[threshold: 1, type: 'NEW', unstable: true]]],
+    pmd: [qualityGates: [[threshold: 1, type: 'NEW', unstable: true]]] )

src/main/java/io/jenkins/plugins/datatables/TableColumn.java

@@ -329,7 +329,8 @@ private String createDefinition() {
                 return mapper.writerWithDefaultPrettyPrinter().writeValueAsString(columnDefinition);
             }
             catch (JsonProcessingException exception) {
-                throw new IllegalArgumentException("Can't convert to JSON: " + columnDefinition);
+                throw new IllegalArgumentException("Can't convert to JSON: " + columnDefinition,
+                        exception);
             }
         }
     }