Added option for empty user agent if the user sets an empty string to work around webview limitations

app/src/main/java/acr/browser/lightning/activity/BrowserActivity.java

@@ -737,7 +737,8 @@ public abstract class BrowserActivity extends ThemableBrowserActivity implements
             if (mSearch.hasFocus()) {
                 searchTheWeb(mSearch.getText().toString());
             }
-        } else if ((keyCode == KeyEvent.KEYCODE_MENU) && (Build.VERSION.SDK_INT <= 16)
+        } else if ((keyCode == KeyEvent.KEYCODE_MENU)
+                && (Build.VERSION.SDK_INT <= Build.VERSION_CODES.JELLY_BEAN)
                 && (Build.MANUFACTURER.compareTo("LGE") == 0)) {
             // Workaround for stupid LG devices that crash
             return true;
@@ -747,7 +748,8 @@ public abstract class BrowserActivity extends ThemableBrowserActivity implements
 
     @Override
     public boolean onKeyUp(int keyCode, @NonNull KeyEvent event) {
-        if ((keyCode == KeyEvent.KEYCODE_MENU) && (Build.VERSION.SDK_INT <= 16)
+        if ((keyCode == KeyEvent.KEYCODE_MENU)
+                && (Build.VERSION.SDK_INT <= Build.VERSION_CODES.JELLY_BEAN)
                 && (Build.MANUFACTURER.compareTo("LGE") == 0)) {
             // Workaround for stupid LG devices that crash
             openOptionsMenu();

app/src/main/java/acr/browser/lightning/view/LightningView.java

@@ -365,7 +365,11 @@ public class LightningView {
                 settings.setUserAgentString(Constants.MOBILE_USER_AGENT);
                 break;
             case 4:
-                settings.setUserAgentString(mPreferences.getUserAgentString(mDefaultUserAgent));
+                String ua = mPreferences.getUserAgentString(mDefaultUserAgent);
+                if (ua == null || ua.isEmpty()) {
+                    ua = " ";
+                }
+                settings.setUserAgentString(ua);
                 break;
         }
     }