TransportHttp: Fix comparison of size with ">= 0"

Error Prone reports:

  [SizeGreaterThanOrEqualsZero] Comparison of a size >= 0 is always true,
  did you intend to check for non-emptiness?

  see https://errorprone.info/bugpattern/SizeGreaterThanOrEqualsZero

Change-Id: Ie964771cacca4b15569eb45f6e273ad2a7e2e49c
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

org.eclipse.jgit/src/org/eclipse/jgit/transport/TransportHttp.java

@@ -952,7 +952,7 @@ public class TransportHttp extends HttpTransport implements WalkTransport,
 				cookieHeaderValue.append(cookie.toString());
 			}
 		}
-		if (cookieHeaderValue.length() >= 0) {
+		if (cookieHeaderValue.length() > 0) {
 			conn.setRequestProperty(HDR_COOKIE, cookieHeaderValue.toString());
 		}
 	}