Fixed several NPEs in the Fetch CLI

The Fetch command line was failing with NPE in case some options were omitted.
Additionally, it was setting a negative timeout when no timeout option was used
which caused HttpURLConnection to throw an IllegalArgumentException.

Change-Id: I2c67e2e1a03044284d183d73f0b82bb7ff79de95
Signed-off-by: Sasa Zivkov <sasa.zivkov@sap.com>
Signed-off-by: Chris Aniszczyk <caniszczyk@gmail.com>

org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/Fetch.java

@@ -93,12 +93,17 @@ class Fetch extends AbstractFetchCommand {
 	protected void run() throws Exception {
 		Git git = new Git(db);
 		FetchCommand fetch = git.fetch();
+		if (fsck != null)
 			fetch.setCheckFetchedObjects(fsck.booleanValue());
+		if (prune != null)
 			fetch.setRemoveDeletedRefs(prune.booleanValue());
+		if (toget != null)
 			fetch.setRefSpecs(toget);
+		if (0 <= timeout)
 			fetch.setTimeout(timeout);
 		fetch.setDryRun(dryRun);
 		fetch.setRemote(remote);
+		if (thin != null)
 			fetch.setThin(thin.booleanValue());
 		fetch.setProgressMonitor(new TextProgressMonitor());