Support java source property being discovered as 1.x (#416)

Author: gnodet

modello-maven-plugin/src/main/java/org/codehaus/modello/maven/AbstractModelloSourceGeneratorMojo.java

@@ -94,13 +94,12 @@ protected void customizeParameters(Properties parameters) {
             parameters.setProperty(ModelloParameterConstants.ENCODING, encoding);
         }
 
-        if (javaSource != null) {
-            if (javaSource.startsWith("1.")) {
-                javaSource = javaSource.substring("1.".length());
-            }
-        } else {
+        if (javaSource == null) {
             javaSource = discoverJavaSource();
         }
+        if (javaSource.startsWith("1.")) {
+            javaSource = javaSource.substring("1.".length());
+        }
         getLog().debug("javaSource=" + javaSource);
         parameters.setProperty(ModelloParameterConstants.OUTPUT_JAVA_SOURCE, javaSource);