fix corner case in awaits & side_effects

fixes #5070

lib/compress.js

@@ -7820,6 +7820,7 @@ merge(Compressor.prototype, {
                     if (abort) return true;
                     if (tw.parent() === exp && node.may_throw(compressor)) return abort = true;
                     if (node instanceof AST_Await) return abort = true;
+                    if (node instanceof AST_ForAwaitOf) return abort = true;
                     if (node instanceof AST_Return) {
                         if (node.value && !is_primitive(compressor, node.value)) return abort = true;
                         return;

test/compress/awaits.js

@@ -2023,3 +2023,26 @@ issue_5034: {
     expect_stdout: "PASS"
     node_version: ">=8"
 }
+
+issue_5070: {
+    options = {
+        awaits: true,
+        side_effects: true,
+    }
+    input: {
+        (async function() {
+            try {
+                for await (var a of console.log("PASS"));
+            } catch (e) {}
+        })();
+    }
+    expect: {
+        (async function() {
+            try {
+                for await (var a of console.log("PASS"));
+            } catch (e) {}
+        })();
+    }
+    expect_stdout: "PASS"
+    node_version: ">=10"
+}