fix: flutter: tabbar and image

[Tiagoperes]

Related Issues

#1643
closes #1660

Description and Example

• The contract states that onTabChange receives a single Int as parameter. The component was passing an object with the property value: Int. It has been fixed.
• There were many problems related to the absence of verifications for nulls. They have all been fixed (I hope).
• Renamed TabBar.TabBarItem.path to TabBar.TabBarItem.icon so it's the same as the component's description in the documentation.
• Replaced the logic to build an Icon inside the TabBar by the BeagleImage component, which already contains this logic.
• Fixed the icon size in the TabBar to 32px height.
• Added style to the component BeagleImage so the image size can be parametrized. Currently, only UnitType.REAL is supported.
• The default mode for the BeagleImage was CENTER. For all other platforms, the default is FIT_CENTER, so I changed it. There is a problem regarding the mode FIT_CENTER, I created an issue for this.
• Added error log to the BeagleImage component when the mobileId is not found.
• Fixed [Flutter] No error logging when component fails to render #1660: now, when an error happens inside the function to build a component, it gets logged. Instead of doing nothing, it returns an UndefinedComponent.
• The tests have been updated to reflect these changes.

Checklist

Please, check if these important points are met using [x]:

• I read the PR Guide and followed the process outlined there for submitting this PR.
• I avoided breaking changes by not changing public APIs that people rely on.
• I am willing to follow-up on review comments in a timely manner.
• I have made the documentation changes or I created an issue explaining how to document this change on Docs issues. Please link the issue here: