Compiler panic in codegen: `index out of bounds: the len is 0 but the index is 0` in `dead_storage::reaching_definitions`

[jubnzv]

The compiler panics with index out of bounds: the len is 0 but the index is 0 in src/codegen/dead_storage.rs (reaching_definitions) when a Yul for loop's body consists only of a continue. The lowering produces a basic block whose block_vars entry is an empty Vec<ReachingDefs>, and the dataflow code unconditionally indexes [0] into it.

MRE:

contract C {
    function f() public pure {
        assembly {
            for { let i := 0 } lt(i, 1) { i := add(i, 1) } { continue }
        }
    }
}

Reproduce: save as mre.sol, run solang compile --target polkadot mre.sol.

Output:

thread 'main' panicked at src/codegen/dead_storage.rs:NNN:
index out of bounds: the len is 0 but the index is 0
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

Expected behavior: codegen handles the empty-body / bare-continue Yul for loop without panicking (the loop is a no-op and should compile cleanly).

Reproduces on all three targets that support Yul (polkadot, solana, evm).

Git commit: 901bfb9
Build: release
rustc 1.96.0-nightly (562dee482 2026-03-21)