Make missing project descriptions an empty file

If a project description is not filled in it should be an empty
file, not a 1 byte file containing only a blank line.

Signed-off-by: Shawn O. Pearce <sop@google.com>

src/main/java/com/google/gerrit/server/ProjectAdminServiceImpl.java

@@ -128,7 +128,10 @@ public class ProjectAdminServiceImpl extends BaseServiceImplementation
             if (f.lock()) {
               String d = proj.getDescription();
               if (d != null) {
-                d = d.trim() + "\n";
+                d = d.trim();
+                if (d.length() > 0) {
+                  d += "\n";
+                }
               } else {
                 d = "";
               }