Fix a panic in table-ops translation

This fixes an issue where `ensure_inserted_block()` wasn't called before
we do some block manipulation in the Wasmtime translation of some
table-related instructions. It looks like `ensure_inserted_block()` is
otherwise called on most instructions being added, so we just need to
call it explicitly it seems here.

Closes #2347

crates/cranelift/src/func_environ.rs

@@ -494,6 +494,7 @@ impl<'module_environment> cranelift_wasm::FuncEnvironment for FuncEnvironment<'m
 
  let reference_type = self.reference_type(WasmType::ExternRef);
 
+ builder.ensure_inserted_block();
  let continue_block = builder.create_block();
  let non_null_elem_block = builder.create_block();
  let gc_block = builder.create_block();
@@ -643,6 +644,7 @@ impl<'module_environment> cranelift_wasm::FuncEnvironment for FuncEnvironment<'m
  // drop the old table element *after* we've replaced it with
  // the new `value`!
 
+ builder.ensure_inserted_block();
  let current_block = builder.current_block().unwrap();
  let inc_ref_count_block = builder.create_block();
  builder.insert_block_after(inc_ref_count_block, current_block);

tests/misc_testsuite/reference-types/no-panic.wast

@@ -0,0 +1,26 @@
+(module
+ (func $test (param i32) (result externref)
+ i32.const 0
+ if
+ else
+ end
+ local.get 0
+ table.get 0
+ )
+ (table 4 externref)
+ (export "test" (func $test))
+)
+
+(module
+ (func $test (param i32)
+ i32.const 0
+ if
+ else
+ end
+ ref.null extern
+ local.get 0
+ table.set 0
+ )
+ (table 4 externref)
+ (export "test" (func $test))
+)