Fixed Dependency version check fails even if required is * (#451)

pf4j/src/main/java/org/pf4j/DefaultVersionManager.java

@@ -39,7 +39,7 @@ public class DefaultVersionManager implements VersionManager {
      */
     @Override
     public boolean checkVersionConstraint(String version, String constraint) {
-        return StringUtils.isNullOrEmpty(constraint) || Version.valueOf(version).satisfies(constraint);
+        return StringUtils.isNullOrEmpty(constraint) || "*".equals(constraint) || Version.valueOf(version).satisfies(constraint);
     }
 
     @Override

pf4j/src/test/java/org/pf4j/DefaultVersionManagerTest.java

@@ -39,6 +39,7 @@ public class DefaultVersionManagerTest {
     public void checkVersionConstraint() {
         assertFalse(versionManager.checkVersionConstraint("1.4.3", ">2.0.0")); // simple
         assertTrue(versionManager.checkVersionConstraint("1.4.3", ">=1.4.0 & <1.6.0")); // range
+        assertTrue(versionManager.checkVersionConstraint("undefined", "*"));
     }
 
     @Test