Improve UT coverage.

src/test/java/org/sonar/runner/LogsTest.java

@@ -67,6 +67,13 @@ public class LogsTest {
     assertThat(baosErr.toString()).contains("ERROR: error");
   }
 
+  @Test
+  public void shouldLogErrorWithoutThrowable() {
+    Logs.error("error", null);
+    assertThat(baosOut.toString()).isEmpty();
+    assertThat(baosErr.toString()).contains("ERROR: error");
+  }
+
   @Test
   public void shouldLogErrorWithThrowable() {
     Logs.error("error", new SonarException());