Fix strcmp treating null and empty strings as equal

common/src/main/java/com/genexus/CommonUtil.java

@@ -19,6 +19,7 @@
 import java.math.BigInteger;
 import java.net.HttpURLConnection;
 import java.net.URL;
+import java.util.Comparator;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
@@ -853,8 +854,12 @@ public static boolean dateCompare( Date left , Date right)
    	public static int strcmp( String left ,
                              String right )
    	{
-               return rtrim(left).compareTo(rtrim(right));
-   	}
+		return Comparator.nullsFirst(String::compareTo)
+			.compare(
+				left  == null ? null : rtrim(left),
+				right == null ? null : rtrim(right)
+			);
+	}
 
    	public static boolean strcmp2( String left ,
                              String right )
@@ -2804,7 +2809,7 @@ else if (className.equals("long") || className.equals("java.lang.Long") || class
         }
         else if (className.equals("string") || className.indexOf("java.lang.String") != -1)
         {
-            return objStr.equals("null") ? null : objStr;
+			return (obj == JSONObject.NULL)? null : objStr;
         }
         else if (className.equals("double") || className.equals("java.lang.Double") || className.equals("[D"))
         {

java/src/test/java/com/genexus/TestCommonUtil.java

@@ -295,7 +295,7 @@ public void testConvertObjectTo() {
 		try{
 			Class stringClass = Class.forName("java.lang.String");
 			result = CommonUtil.convertObjectTo(obj, stringClass, true);
-			Assert.assertEquals(null, result);
+			Assert.assertEquals("null", result);
 		} catch (Exception e){
 			Assert.fail("Test failed " + e);
 		}