Fix try block optimizer bug.

CHANGELOG.md

@@ -13,6 +13,7 @@ Bug fixes
 * The `optimize` command in `rhai-repl` now works properly and cycles through `None`->`Simple`->`Full`.
 * `Engine::call_fn_XXX` no longer return errors unnecessarily wrapped in `EvalAltResult::ErrorInFunctionCall`.
 * Some tests that panic on 32-bit architecture are fixed (thanks [`@alexanderkjall`](https://github.com/alexanderkjall) [851](https://github.com/rhaiscript/rhai/issues/851)).
+* The optimizer no longer goes into an infinite loop when optimizing a `try` statement with an empty body.
 
 Deprecated API's
 ----------------

src/optimizer.rs

@@ -798,8 +798,12 @@ fn optimize_stmt(stmt: &mut Stmt, state: &mut OptimizerState, preserve_result: b
         Stmt::TryCatch(x, ..) if x.body.iter().all(Stmt::is_pure) => {
             // If try block is pure, there will never be any exceptions
             state.set_dirty();
-            *x.body.statements_mut() =
-                optimize_stmt_block(x.body.take_statements(), state, false, true, false);
+            let statements = x.body.take_statements();
+            let block = StmtBlock::new_with_span(
+                optimize_stmt_block(statements, state, false, true, false),
+                x.body.span(),
+            );
+            *stmt = Stmt::Block(block.into());
         }
         // try { try_block } catch ( var ) { catch_block }
         Stmt::TryCatch(x, ..) => {