Some minor cleanups (#1966)

* Some minor cleanups

* Small additions

* Cleanup ExtrinsicEra decoding

* Minor adjustments

* Remove support for metadata v0 parsing

* Adjust refCountDelay

* refCountDelay comments

* Adjust Metadata tests

* Metadata default creation

* Funky lines

* Cleanup as AccountIdAndIndex

* Some derive returns

* Try and cleanup info extraction

packages/metadata/src/Metadata/MagicNumber.ts

@@ -14,8 +14,10 @@ export default class MagicNumber extends U32 {
   constructor (registry: Registry, value?: any) {
     super(registry, value);
 
-    const magic = new U32(registry, MAGIC_NUMBER);
+    if (!this.isEmpty) {
+      const magic = new U32(registry, MAGIC_NUMBER);
 
-    assert(this.eq(magic), `MagicNumber mismatch: expected ${magic.toHex()}, found ${this.toHex()}`);
+      assert(this.eq(magic), `MagicNumber mismatch: expected ${magic.toHex()}, found ${this.toHex()}`);
+    }
   }
 }