fix corner cases in ie8 & side_effects (#4731)

fixes #4729
fixes #4730

test/compress/ie8.js

@@ -2919,3 +2919,28 @@ issue_4568: {
     }
     expect_stdout: "undefined 1"
 }
+
+issue_4729: {
+    options = {
+        ie8: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        try {
+            f;
+        } catch(e) {
+            var a = a && a[function f() {}];
+            console.log("PASS");
+        }
+    }
+    expect: {
+        try {
+            f;
+        } catch(e) {
+            (function f() {});
+            console.log("PASS");
+        }
+    }
+    expect_stdout: "PASS"
+}

test/compress/side_effects.js

@@ -558,3 +558,33 @@ drop_side_effect_free_call: {
     }
     expect_stdout: "PASS"
 }
+
+issue_4730_1: {
+    options = {
+        side_effects: true,
+    }
+    input: {
+        var a;
+        console.log("PASS") + (a && a[a.p]);
+    }
+    expect: {
+        var a;
+        console.log("PASS");
+    }
+    expect_stdout: "PASS"
+}
+
+issue_4730_2: {
+    options = {
+        side_effects: true,
+    }
+    input: {
+        var a;
+        !console.log("PASS") || a && a[a.p];
+    }
+    expect: {
+        var a;
+        console.log("PASS");
+    }
+    expect_stdout: "PASS"
+}