fix corner case in dead_code (#4194)

fixes #4193

lib/compress.js

@@ -6571,14 +6571,17 @@ merge(Compressor.prototype, {
                         });
                     });
                 }
-                [].unshift.apply(body, self.body);
+                body.unshift(make_node(AST_BlockStatement, self, self).optimize(compressor));
-                if (self.bfinally) [].push.apply(body, self.bfinally.body);
+                if (self.bfinally) {
+                    body.push(make_node(AST_BlockStatement, self.bfinally, self.bfinally).optimize(compressor));
+                }
                 return make_node(AST_BlockStatement, self, {
                     body: body
                 }).optimize(compressor);
             }
             if (self.bfinally && has_declarations_only(self.bfinally)) {
-                var body = self.body.concat(self.bfinally.body);
+                var body = make_node(AST_BlockStatement, self.bfinally, self.bfinally).optimize(compressor);
+                body = self.body.concat(body);
                 if (!self.bcatch) return make_node(AST_BlockStatement, self, {
                     body: body
                 }).optimize(compressor);

test/compress/const.js

@@ -725,3 +725,25 @@ issue_4191_2: {
     }
     expect_stdout: "function undefined"
 }
+
+issue_4193: {
+    options = {
+        dead_code: true,
+    }
+    input: {
+        try {} catch (e) {
+            var a;
+        } finally {
+            const a = 0;
+        }
+        console.log(a);
+    }
+    expect: {
+        var a;
+        {
+            const a = 0;
+        }
+        console.log(a);
+    }
+    expect_stdout: true
+}