[JENKINS-19976] Touch-ups to PR #1054.

core/src/main/java/hudson/PluginManager.java

@@ -464,7 +464,11 @@ public abstract class PluginManager extends AbstractModelObject implements OnMas
                 if (d.shortName.equals(p.getShortName())) {
                     // this plugin depends on the newly loaded one!
                     // recalculate dependencies!
-                    getPluginStrategy().updateDependency(depender, p);
+                    try {
+                        getPluginStrategy().updateDependency(depender, p);
+                    } catch (AbstractMethodError x) {
+                        LOGGER.log(WARNING, "{0} does not yet implement updateDependency", getPluginStrategy().getClass());
+                    }
                     break;
                 }
             }