[internal] Hotfix `fmt` crashing on non-formattable targets (#14168)
[internal] Hotfix `fmt` crashing on non-formattable targets (#14168)

We'd try running the `_LanguageFmts` rule on targets with no applicable `FmtRequests`, which is not necessary. It would then crash when trying to call `tgt[SourceFiles]` on the code.

[ci skip-rust]
benjyw/pants,benjyw/pants,benjyw/pants,benjyw/pants,benjyw/pants,pantsbuild/pants,benjyw/pants,pantsbuild/pants,pantsbuild/pants,benjyw/pants,pantsbuild/pants,pantsbuild/pants,pantsbuild/pants,pantsbuild/pants