Skip properly any non numerical value

[xbgmsharp]

derived-data and freeboard-sk-helper plugins generate new entries that can be null or a string. It should be ignored.

• Clean up empty lines and extra space
• Skip sending null values, Error: Expected float value for field value but got null at exports.Point.floatField
• Skip sending non float values, avoid Error: Expected float value for field value but got "string" at exports.Point.floatField