Empty calories goal crashing the app

[RandomUsername1315]

Bugfix

This pr fixes the issu that caused the app to crash if the user set their calories goals as an empty string and navigate back to the main/overview screen. This was fixed by two things : first disabling the saving button in the setting's page if the value for the calory goal is empty and the progression tracker ("the thing with the circle on the main screen") to graph the progress as 0% if it recieves a Nan

[sonarcloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
77.8% Coverage on New Code
0.0% Duplication on New Code

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