Wrap DOMExceptions thrown by base64ToArrayBuffer in ParseError

This fixes the remaining 2 test failures:

- should parse: padding at beginning
- should parse: padding in middle

Author: apasel422

src/parser.ts

@@ -381,7 +381,11 @@ export default class Parser {
       throw new ParseError(this.pos, 'ByteSequence does not contain a valid base64 string');
     }
 
-    return base64ToArrayBuffer(b64Content);
+    try {
+      return base64ToArrayBuffer(b64Content);
+    } catch {
+      throw new ParseError(this.pos, 'ByteSequence does not contain a valid base64 string');
+    }
 
   }