Fix NPE in URIish when parsing an empty URI

Change-Id: Id1c42dc9843f62c581b9904b02150de53cf7777c
Signed-off-by: Chris Aniszczyk <caniszczyk@gmail.com>

org.eclipse.jgit.test/tst/org/eclipse/jgit/transport/URIishTest.java

@@ -62,6 +62,26 @@ public class URIishTest {
 
 	private static final String GIT_SCHEME = "git://";
 
+	@Test
+	public void shouldRaiseErrorOnEmptyURI() throws Exception {
+		try {
+			new URIish("");
+			fail("expecting an exception");
+		} catch (URISyntaxException e) {
+			// expected
+		}
+	}
+
+	@Test
+	public void shouldRaiseErrorOnNullURI() throws Exception {
+		try {
+			new URIish((String) null);
+			fail("expecting an exception");
+		} catch (URISyntaxException e) {
+			// expected
+		}
+	}
+
 	@Test
 	public void testUnixFile() throws Exception {
 		final String str = "/home/m y";

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

@@ -55,6 +55,7 @@ import java.util.regex.Pattern;
 
 import org.eclipse.jgit.JGitText;
 import org.eclipse.jgit.lib.Constants;
+import org.eclipse.jgit.util.StringUtils;
 
 /**
  * This URI like construct used for referencing Git archives over the net, as
@@ -193,6 +194,10 @@ public class URIish implements Serializable {
 	 * @throws URISyntaxException
 	 */
 	public URIish(String s) throws URISyntaxException {
+		if (StringUtils.isEmptyOrNull(s)) {
+			throw new URISyntaxException("The uri was empty or null",
+					JGitText.get().cannotParseGitURIish);
+		}
 		Matcher matcher = SINGLE_SLASH_FILE_URI.matcher(s);
 		if (matcher.matches()) {
 			scheme = matcher.group(1);

org.eclipse.jgit/src/org/eclipse/jgit/util/StringUtils.java

@@ -222,4 +222,15 @@ public final class StringUtils {
 	private StringUtils() {
 		// Do not create instances
 	}
+
+	/**
+	 * Test if a string is empty or null.
+	 *
+	 * @param stringValue
+	 *            the string to check
+	 * @return <code>true</code> if the string is <code>null</code> or empty
+	 */
+	public static boolean isEmptyOrNull(String stringValue) {
+		return stringValue == null || stringValue.length() == 0;
+	}
 }