install baserom before splitting assets

src/main/java/app/Environment.java

···
 import project.ProjectListing;
 import project.ProjectManager;
 import project.Manifest;
+import project.engine.BuildException;
+import project.engine.Engine;
 import project.ui.ProjectSwitcherDialog;
 import assets.AssetExtractor;
 import assets.ExpectedAsset;
···
 		}
 
 		Directories.setProjectDirectory(project.getPath());
-		Directories.setDumpDirectory(project.getEngine().getDumpDir().getAbsolutePath());
+		final Engine engine = project.getEngine();
+		Directories.setDumpDirectory(engine.getDumpDir().getAbsolutePath());
+
+		usBaseRom = engine.getBaseRom();
+		if (!usBaseRom.exists()) {
+			promptForBaserom();
+			if (!usBaseRom.exists())
+				return false;
+		}
+
+		try {
+			engine.splitAssets();
+		} catch (BuildException e) {
+			Logger.logError("Failed to split assets: " + e.getMessage());
+			return false;
+		}
 
 		// Asset stack (TODO: move to Project?)
 		assetDirectories = new ArrayList<>();
···
 		// ...dependencies...
 		assetDirectories.add(Directories.ENGINE_ASSETS_US.toFile());
 
-		usBaseRom = project.getEngine().getBaseRom();
-		if (!usBaseRom.exists())
-			promptForBaserom();
 		if (!ensureDumpExtracted()) {
 			return false;
 		}

src/main/java/project/engine/Engine.java

···
 			else
 				checkoutRef();
 		}
-
-		splitAssets(); // TODO: only call when necessary i.e. git HEAD changed
 	}
 
 	/**
···
 		buildEnv.gitCheckout(directory, ref, BuildOutputListener.toLogger());
 	}
 
-	public BuildResult splitAssets() throws BuildException, IOException
+	public void splitAssets() throws BuildException, IOException
 	{
 		Logger.log("Splitting assets from ROM...", Priority.MILESTONE);
-		return buildEnv.configure(directory, BuildOutputListener.toLogger());
+		BuildResult result = buildEnv.configure(directory, BuildOutputListener.toLogger());
+		if (!result.isSuccess())
+			throw new BuildException("Failed to split assets: " + result.getErrorMessage());
 	}
 
 	private static boolean isGitRepo(File dir)