Remove extra-check for staleSources is non-null
diff --git a/src/main/java/org/apache/maven/plugin/compiler/AbstractCompilerMojo.java b/src/main/java/org/apache/maven/plugin/compiler/AbstractCompilerMojo.java
index 703b9aa..48a152a 100644
--- a/src/main/java/org/apache/maven/plugin/compiler/AbstractCompilerMojo.java
+++ b/src/main/java/org/apache/maven/plugin/compiler/AbstractCompilerMojo.java
@@ -1344,7 +1344,7 @@
                 getLog().debug( "Stale source detected: " + f.getAbsolutePath() );
             }
         }
-        return staleSources != null && !staleSources.isEmpty();
+        return !staleSources.isEmpty();
     }