Run setIndex when revisionState==null

The setIndex is not called when open exisiting job's
manifest information. At that time, revisionState==null,
and the manifest cannot be fetched. The repo manifest
information is blank on web.

The fix just calls setIndex when revisionState==null
before get manifest.

src/main/java/hudson/plugins/repo/ManifestAction.java

@@ -136,27 +136,43 @@ public final String getUrlName() {
 	 * Gets a String representation of the static manifest for this repo snapshot.
 	 */
 	public String getManifest() {
+		if (revisionState == null) {
+			setIndex(index);
+		}
+
 		return revisionState == null ? "" : revisionState.getManifest();
 	}
 
 	/**
 	 * Returns the manifest repository's url for this repo snapshot.
 	 */
 	public String getUrl() {
+		if (revisionState == null) {
+			setIndex(index);
+		}
+
 		return revisionState == null ? "" : revisionState.getUrl();
 	}
 
 	/**
 	 * Returns the manifest repository's branch name for this repo snapshot.
 	 */
 	public String getBranch() {
+		if (revisionState == null) {
+			setIndex(index);
+		}
+
 		return revisionState == null ? "" : revisionState.getBranch();
 	}
 
 	/**
 	 * Returns the path to the manifest file for this repo snapshot.
 	 */
 	public String getFile() {
+		if (revisionState == null) {
+			setIndex(index);
+		}
+
 		return revisionState == null ? "" : revisionState.getFile();
 	}
 }