Fixes Issue 733: unvalidated BigInteger for LED hex value

[rgomezp]

• Handles incorrect ledColor hex value, sets default, throws warning
• Unit test checks that the hex value is set to the default and warning was shown

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This change is 

[jkasten2]

Reviewed 1 of 3 files at r1.
Reviewable status: 1 of 3 files reviewed, 3 unresolved discussions (waiting on @jkasten2 and @rgomezp)

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OneSignalSDK/onesignal/src/main/java/com/onesignal/NotificationChannelManager.java, line 136 at r1 (raw file):

      if (payload.has("ledc")){
         Pattern pattern = Pattern.compile(HEX_PATTERN);

Compile pattern in a static instead of compiling

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OneSignalSDK/onesignal/src/main/java/com/onesignal/NotificationChannelManager.java, line 142 at r1 (raw file):

         BigInteger ledColor;

         if ( !matcher.matches() ) {

nit, remove spaces inside ( )

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OneSignalSDK/onesignal/src/main/java/com/onesignal/NotificationChannelManager.java, line 150 at r1 (raw file):

            ledColor = new BigInteger(ledc, 16);
            channel.setLightColor(ledColor.intValue());
         } catch (Throwable t){

Missing spaces between ){

[jkasten2]

Reviewed 2 of 2 files at r3.
Reviewable status: complete! all files reviewed, all discussions resolved