fix: fixed crash in PowerSourceActivity by adding checks to input values

[AsCress]

Fixes #2484

Changes

• Adds checks to values input through EditTexts in the PowerSourceActivity to check whether they are float parseable or not. Resets voltage value to default in the later case.

Screenshots / Recordings

Screen_recording_20240615_213310.mp4

Checklist:

• No hard coding: I have used resources from strings.xml, dimens.xml and colors.xml without hard coding any value.
• No end of file edits: No modifications done at end of resource files strings.xml, dimens.xml or colors.xml.
• Code reformatting: I have reformatted code and fixed indentation in every file included in this pull request.
• No extra space: My code does not contain any extra lines or extra spaces than the ones that are necessary.

@marcnause Could you please confirm if this issue is completely fixed now ?