Various optimizations related to library extraction.

Updated PackXZExtract to v1.0.1.
If no files are queued for extraction, the step is skipped.
The UI now shows some indication that the extraction is in progress.

app/assets/js/assetguard.js

@@ -1574,11 +1574,15 @@ class AssetGuard extends EventEmitter {
                 self.progress -= self[identifier].dlsize
                 self[identifier] = new DLTracker([], 0)
                 if(self.totaldlsize === 0) {
-                    self.emit('extracting')
-                    AssetGuard._extractPackXZ(self.extractQueue, self.javaexec).then(() => {
-                        self.extractQueue = []
+                    if(self.extractQueue.length > 0){
+                        self.emit('extracting')
+                        AssetGuard._extractPackXZ(self.extractQueue, self.javaexec).then(() => {
+                            self.extractQueue = []
+                            self.emit('dlcomplete')
+                        })
+                    } else {
                         self.emit('dlcomplete')
-                    })
+                    }
                 }
             })
             return true