Mark the getIdeHookState prop as optional.

Author: nedtwigg

Diff for: plugin-gradle/src/main/java/com/diffplug/gradle/spotless/SpotlessTaskImpl.java

@@ -34,6 +34,7 @@
 import org.gradle.api.tasks.CacheableTask;
 import org.gradle.api.tasks.Input;
 import org.gradle.api.tasks.Internal;
+import org.gradle.api.tasks.Optional;
 import org.gradle.api.tasks.TaskAction;
 import org.gradle.work.ChangeType;
 import org.gradle.work.FileChange;
@@ -49,6 +50,7 @@
 @CacheableTask
 public abstract class SpotlessTaskImpl extends SpotlessTask {
 	@Input
+	@Optional
 	abstract Property<IdeHook.State> getIdeHookState();
 
 	@Internal