Description

Fixes #7625

forc-fmt collapses empty if-body + else onto a single line:

// Before (wrong):
if __size_of::<T>() == 0 {    } else if __is_reference_type::<T>() {

// After (correct):
if __size_of::<T>() == 0 {
} else if __is_reference_type::<T>() {

Root cause: In format_then_block, when the then-block is empty and has an else clause, block_unindent() was called but no newline was written — so the closing } from format_else_opt ended up on the same line.

Fix: Write a newline after the empty body when an else clause exists, and skip block_unindent since close_curly_brace in format_else_opt already handles unindentation. Guarded with LineStyle::Inline to avoid injecting newlines during width measurement probes.

Checklist

• I have linked to any relevant issues.
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