Fixes #1481 no problems found results in blank file instead of empty xml

pmd-core/src/main/java/net/sourceforge/pmd/cpd/CPDCommandLineInterface.java

@@ -86,8 +86,8 @@ public class CPDCommandLineInterface {
                 }
 
 		cpd.go();
+		System.out.println(arguments.getRenderer().render(cpd.getMatches()));
 		if (cpd.getMatches().hasNext()) {
-			System.out.println(arguments.getRenderer().render(cpd.getMatches()));
 			setStatusCodeOrExit(DUPLICATE_CODE_FOUND);
 		}
 	}

pmd-core/src/test/java/net/sourceforge/pmd/cpd/CPDCommandLineInterfaceTest.java

@@ -0,0 +1,33 @@
+/**
+ * BSD-style license; for more info see http://pmd.sourceforge.net/license.html
+ */
+
+package net.sourceforge.pmd.cpd;
+
+import org.junit.Assert;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.contrib.java.lang.system.LogMode;
+import org.junit.contrib.java.lang.system.RestoreSystemProperties;
+import org.junit.contrib.java.lang.system.StandardOutputStreamLog;
+import org.junit.rules.TestRule;
+
+public class CPDCommandLineInterfaceTest {
+    @Rule
+    public final TestRule restoreSystemProperties = new RestoreSystemProperties();
+    @Rule
+    public final StandardOutputStreamLog log = new StandardOutputStreamLog(LogMode.LOG_ONLY);
+
+    @Test
+    public void testEmptyResultRendering() {
+        System.setProperty(CPDCommandLineInterface.NO_EXIT_AFTER_RUN, "true");
+        CPDCommandLineInterface.main(new String[] {
+                "--minimum-tokens", "340",
+                "--language", "java",
+                "--files", "src/test/resources/net/sourceforge/pmd/cpd/files/",
+                "--format", "xml"
+        });
+        Assert.assertEquals("<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n<pmd-cpd/>\n", log.getLog());
+    }
+
+}

src/site/markdown/overview/changelog.md

@@ -16,6 +16,8 @@
 
 *   java-unusedcode/UnusedLocalVariable
     *   [#1484](https://sourceforge.net/p/pmd/bugs/1484/): UnusedLocalVariable - false positive - parenthesis
+*   General
+    *   [#1481](https://sourceforge.net/p/pmd/bugs/1481/): no problems found results in blank file instead of empty xml
 
 **API Changes:**