fix: accept empty resources.arsc

[IgorEisberg]

Apktool treats APKs with stub resources.arsc like criminals:

I: Loading resource table...
Exception in thread "main" brut.androlib.AndrolibException: arsc files with zero packages or no arsc file found.
        at brut.androlib.res.AndrolibResources.loadMainPkg(AndrolibResources.java:84)
        at brut.androlib.res.AndrolibResources.getResTable(AndrolibResources.java:56)
        at brut.androlib.Androlib.getResTable(Androlib.java:74)
        at brut.androlib.ApkDecoder.getResTable(ApkDecoder.java:270)
        at brut.androlib.ApkDecoder.decode(ApkDecoder.java:110)
        at brut.apktool.Main.cmdDecode(Main.java:175)
        at brut.apktool.Main.main(Main.java:79)

But in fact, those APKs are valid and very common among overlay APKs, but here's a non-overlay example as well:
https://drive.google.com/file/d/1seAnndB9cH6_qo04FC7_1JPW5CVXLMnt/view

This change creates a "fake ResPackage", exactly as done in decodeManifest, if resources.arsc was loaded but contains 0 packages.
The output is valid and recompilation already produces an identical 40 bytes stub resources.arsc without any additional changes needed.

P.S. also fixed a few missing spaces for cleanliness.

[iBotPeaches]

Thanks. Looks good.

[IgorEisberg]

A note to anyone who plans to inject any resources to a empty APK like that:
By being empty, these packages don't have a package ID at all, so you'll see this in apktool.yml:

packageInfo: null

If you plan on adding resources and naturally your resource IDs are prefixed with package ID 0x7f, you'll have to update this line in apktool.yml to:

packageInfo:
  forcedPackageId: '127'
  renameManifestPackage: null

[IgorEisberg]

Small tweak to make sure apktool.yml doesn't falsely state "isFrameworkApk: true" when it should be "false" for empty packages.

[iBotPeaches]

thanks again - merged/changelog updated.