fix corner case in awaits (#4988)

fixes #4987

lib/compress.js

@@ -319,10 +319,12 @@ merge(Compressor.prototype, {
                     }),
                 });
             }
-            if (node instanceof AST_Lambda && node !== self) {
-                return node;
-            }
             if (node instanceof AST_Block) {
+                if (node instanceof AST_Lambda) {
+                    if (node !== self) return node;
+                } else if (insert === "awaits" && node instanceof AST_Try) {
+                    if (node.bfinally) return node;
+                }
                 var index = node.body.length - 1;
                 if (index >= 0) {
                     node.body[index] = node.body[index].transform(tt);
@@ -7587,7 +7589,7 @@ merge(Compressor.prototype, {
                 });
             }
             if (async && compressor.option("awaits")) {
-                if (drop_body) exp.process_expression(true, function(node) {
+                if (drop_body) exp.process_expression("awaits", function(node) {
                     var body = node.body;
                     if (body instanceof AST_Await) {
                         if (is_primitive(compressor, body.expression)) {

test/compress/awaits.js

@@ -1726,3 +1726,35 @@ issue_4975: {
     expect_stdout: "object"
     node_version: ">=8"
 }
+
+issue_4987: {
+    options = {
+        awaits: true,
+        side_effects: true,
+    }
+    input: {
+        (async function() {
+            try {
+                await 42;
+            } finally {
+                console.log("foo");
+            }
+        })();
+        console.log("bar");
+    }
+    expect: {
+        (async function() {
+            try {
+                await 0;
+            } finally {
+                console.log("foo");
+            }
+        })();
+        console.log("bar");
+    }
+    expect_stdout: [
+        "bar",
+        "foo",
+    ]
+    node_version: ">=8"
+}