JavaScript: handle propertyAssignment.modifiers being empty

[greg-at-moderne]

What's changed?

Adding a null-safety guard for propertyAssignment.modifiers in JavaScript's visitor logic.

What's your motivation?

Otherwise this tends to be observed, for instance in the auto formatter:

java.util.concurrent.CompletionException: io.moderne.jsonrpc.JsonRpcException: {code=-32603, message='Request Visit failed with message: TypeError: Cannot read properties of undefined (reading 'length')
    at mapAsync (/opt/moderne/cli/recipes/npm/bundled/8.91.5/node_modules/@openrewrite/rewrite/src/util.ts:19:29)
    at NormalizeWhitespaceVisitor.visitPropertyAssignment (/opt/moderne/cli/recipes/npm/bundled/8.91.5/node_modules/@openrewrite/rewrite/src/javascript/visitor.ts:554:38)