BUGFIX: Skipping accounts if none exist.

[kilogold]

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This could include other PRs this PR is built on top of; API breaking changes; reasons for why the PR is on hold; or anything else you would like to draw attention to.

Status	Type	⚠️ Core Change	Issue
Ready	Bug	No	(N/A)

Problem

Unhandled exception. System.NullReferenceException: Object reference not set to an instance of an object.
   at AnchorSourceGenerator.<>c.<Main>b__0_1(CommandLineOptions opts) in /Users/gabrielepicco/Documents/Solana/Solana.Unity.Anchor/Solana.Unity.Anchor.Tool/AnchorSourceGenerator.cs:line 102
   at CommandLine.ParserResultExtensions.MapResult[TSource,TResult](ParserResult`1 result, Func`2 parsedFunc, Func`2 notParsedFunc)
   at AnchorSourceGenerator.Main(String[] args) in /Users/gabrielepicco/Documents/Solana/Solana.Unity.Anchor/Solana.Unity.Anchor.Tool/AnchorSourceGenerator

Building simple Anchor programs solely using token accounts from anchor-spl will require no additional structs with
#[account] attribute. The parser throws an exception when unable to find the "accounts" attribute in the JSON IDL.

Even an empty Anchor project may be affected (not tested).

Workaround

Add a dummy struct to the Anchor program for populating the IDL fields. For example:

#[account]
pub struct Dummy{
    pub data: u64,
}

Solution

Skip "accounts" token if missing in the IDL.

[kilogold]

If could have done a simple "if" check, but I chose the least invasive change for simpler review.

[GabrielePicco]

Thanks @kilogold , LGTM