Update main.js

On my first attempts to run this with my projects layers (note: not using rarity delimiter), the code would error with the stack trace that follows. This change made my code work, but this PR is to point out the issue more than to propose that this is the perfect solution.

```UnhandledPromiseRejectionWarning: TypeError: Cannot read property 'split' of undefined
    at cleanDna (/Users/christopherfoley/nft/hashlips_art_engine/src/main.js:54:25)
    at /Users/christopherfoley/nft/hashlips_art_engine/src/main.js:151:22```

Author: chrisninetyone

src/main.js

@@ -45,7 +45,7 @@ const getRarityWeight = (_str) => {
     nameWithoutExtension.split(rarityDelimiter).pop()
   );
   if (isNaN(nameWithoutWeight)) {
-    nameWithoutWeight = 0;
+    nameWithoutWeight = 1;
   }
   return nameWithoutWeight;
 };