Fix SpaceSafeURI nullability issues

src/main/kotlin/link/infra/packwiz/installer/DownloadTask.kt

@@ -183,7 +183,7 @@ internal class DownloadTask private constructor(val metadata: IndexFile.File, de
 				// isDirectory follows symlinks, but createDirectories doesn't
 				try {
 					Files.createDirectories(destPath.parent)
-				} catch (e: FileAlreadyExistsException) {
+				} catch (e: java.nio.file.FileAlreadyExistsException) {
 					if (!Files.isDirectory(destPath.parent)) {
 						throw e
 					}

src/main/kotlin/link/infra/packwiz/installer/UpdateManager.kt

@@ -21,7 +21,6 @@ import link.infra.packwiz.installer.ui.IUserInterface.ExceptionListResult
 import link.infra.packwiz.installer.ui.data.InstallProgress
 import link.infra.packwiz.installer.util.Log
 import link.infra.packwiz.installer.util.ifletOrErr
-import link.infra.packwiz.installer.util.ifletOrWarn
 import okio.buffer
 import java.io.FileNotFoundException
 import java.io.FileReader
@@ -29,7 +28,6 @@ import java.io.FileWriter
 import java.io.IOException
 import java.nio.file.Files
 import java.nio.file.Paths
-import java.util.*
 import java.util.concurrent.CompletionService
 import java.util.concurrent.ExecutionException
 import java.util.concurrent.ExecutorCompletionService
@@ -194,7 +192,8 @@ class UpdateManager internal constructor(private val opts: Options, val ui: IUse
 			handleCancellation()
 		}
 		try {
-			ifletOrWarn(pf.index, "No index file found") { index ->
+			// TODO: switch to OkHttp for better redirect handling
+			ui.ifletOrErr(pf.index, "No index file found, or the pack file is empty; note that Java doesn't automatically follow redirects from HTTP to HTTPS (and may cause this error)") { index ->
 				ui.ifletOrErr(index.hashFormat, index.hash, "Pack has no hash or hashFormat for index") { hashFormat, hash ->
 					ui.ifletOrErr(getNewLoc(opts.downloadURI, index.file), "Pack has invalid index file: " + index.file) { newLoc ->
 						processIndex(

src/main/kotlin/link/infra/packwiz/installer/metadata/IndexFile.kt

@@ -78,9 +78,9 @@ class IndexFile {
 			get() {
 				if (metafile) {
 					return linkedFile?.name ?: linkedFile?.filename ?:
-					file?.run { Paths.get(path).fileName.toString() } ?: "Invalid file"
+					file?.run { Paths.get(path ?: return "Invalid file").fileName.toString() } ?: "Invalid file"
 				}
-				return file?.run { Paths.get(path).fileName.toString() } ?: "Invalid file"
+				return file?.run { Paths.get(path ?: return "Invalid file").fileName.toString() } ?: "Invalid file"
 			}
 
 		// TODO: URIs are bad

src/main/kotlin/link/infra/packwiz/installer/metadata/SpaceSafeURI.kt

@@ -32,7 +32,7 @@ class SpaceSafeURI : Comparable<SpaceSafeURI>, Serializable {
 		)
 	}
 
-	val path: String get() = u.path.replace("%20", " ")
+	val path: String? get() = u.path?.replace("%20", " ")
 
 	override fun toString(): String = u.toString().replace("%20", " ")
 
@@ -52,9 +52,9 @@ class SpaceSafeURI : Comparable<SpaceSafeURI>, Serializable {
 
 	override fun compareTo(other: SpaceSafeURI): Int = u.compareTo(other.u)
 
-	val scheme: String get() = u.scheme
-	val authority: String get() = u.authority
-	val host: String get() = u.host
+	val scheme: String? get() = u.scheme
+	val authority: String? get() = u.authority
+	val host: String? get() = u.host
 
 	@Throws(MalformedURLException::class)
 	fun toURL(): URL = u.toURL()

src/main/kotlin/link/infra/packwiz/installer/request/handlers/RequestHandlerGithub.kt

@@ -1,7 +1,6 @@
 package link.infra.packwiz.installer.request.handlers
 
 import link.infra.packwiz.installer.metadata.SpaceSafeURI
-import java.util.*
 import java.util.concurrent.locks.ReentrantReadWriteLock
 import java.util.regex.Pattern
 import kotlin.concurrent.read
@@ -21,7 +20,7 @@ class RequestHandlerGithub : RequestHandlerZip(true) {
 	private val zipUriMap: MutableMap<String, SpaceSafeURI> = HashMap()
 	private val zipUriLock = ReentrantReadWriteLock()
 	private fun getRepoName(loc: SpaceSafeURI): String? {
-		val matcher = repoMatcherPattern.matcher(loc.path)
+		val matcher = repoMatcherPattern.matcher(loc.path ?: return null)
 		return if (matcher.matches()) {
 			matcher.group(1)
 		} else {
@@ -47,7 +46,7 @@ class RequestHandlerGithub : RequestHandlerZip(true) {
 	}
 
 	private fun getBranch(loc: SpaceSafeURI): String? {
-		val matcher = branchMatcherPattern.matcher(loc.path)
+		val matcher = branchMatcherPattern.matcher(loc.path ?: return null)
 		return if (matcher.matches()) {
 			matcher.group(1)
 		} else {
@@ -66,6 +65,6 @@ class RequestHandlerGithub : RequestHandlerZip(true) {
 			return false
 		}
 		// TODO: more match testing?
-		return "github.com" == loc.host && branchMatcherPattern.matcher(loc.path).matches()
+		return "github.com" == loc.host && branchMatcherPattern.matcher(loc.path ?: return false).matches()
 	}
 }