LogBox: do less work in production when LogBox shouldn't even be running

Summary:
Do we need this? Is it possible for any of these codepaths to execute in production? If so, it would be nice to avoid NPEs or even scheduling work on the UI thread.

Maybe we want to add soft exception logging for if these paths are called?

Changelog: [Internal] make sure LogBox does even less work when it's not hooked up

Reviewed By: rickhanlonii

Differential Revision: D20156812

fbshipit-source-id: ba9faedcb3b0951e6913724ca99549dc2d16237e

Author: JoshuaGross

ReactAndroid/src/main/java/com/facebook/react/devsupport/LogBoxModule.java

@@ -32,11 +32,12 @@ public LogBoxModule(ReactApplicationContext reactContext, DevSupportManager devS
     super(reactContext);
 
     mDevSupportManager = devSupportManager;
+
     UiThreadUtil.runOnUiThread(
         new Runnable() {
           @Override
           public void run() {
-            if (mReactRootView == null) {
+            if (mReactRootView == null && mDevSupportManager != null) {
               mReactRootView = mDevSupportManager.createRootView("LogBox");
               if (mReactRootView == null) {
                 FLog.e(
@@ -55,25 +56,27 @@ public String getName() {
 
   @Override
   public void show() {
-    UiThreadUtil.runOnUiThread(
-        new Runnable() {
-          @Override
-          public void run() {
-            if (mLogBoxDialog == null && mReactRootView != null) {
-              Activity context = getCurrentActivity();
-              if (context == null || context.isFinishing()) {
-                FLog.e(
-                    ReactConstants.TAG,
-                    "Unable to launch logbox because react activity "
-                        + "is not available, here is the error that logbox would've displayed: ");
-                return;
+    if (mReactRootView != null) {
+      UiThreadUtil.runOnUiThread(
+          new Runnable() {
+            @Override
+            public void run() {
+              if (mLogBoxDialog == null && mReactRootView != null) {
+                Activity context = getCurrentActivity();
+                if (context == null || context.isFinishing()) {
+                  FLog.e(
+                      ReactConstants.TAG,
+                      "Unable to launch logbox because react activity "
+                          + "is not available, here is the error that logbox would've displayed: ");
+                  return;
+                }
+                mLogBoxDialog = new LogBoxDialog(context, mReactRootView);
+                mLogBoxDialog.setCancelable(false);
+                mLogBoxDialog.show();
               }
-              mLogBoxDialog = new LogBoxDialog(context, mReactRootView);
-              mLogBoxDialog.setCancelable(false);
-              mLogBoxDialog.show();
             }
-          }
-        });
+          });
+    }
   }
 
   @Override
@@ -83,7 +86,7 @@ public void hide() {
           @Override
           public void run() {
             if (mLogBoxDialog != null) {
-              if (mReactRootView.getParent() != null) {
+              if (mReactRootView != null && mReactRootView.getParent() != null) {
                 ((ViewGroup) mReactRootView.getParent()).removeView(mReactRootView);
               }
               mLogBoxDialog.dismiss();