Berry avoid tasmota.wifi() returning bad values when wifi is turned off

[s-hadinger]

Description:

When the wifi is turned off, there is a short time when tasmota.wifi('up') is true but wifi values are not available. This fix prevents it.

Checklist:

• The pull request is done against the latest development branch
• Only relevant files were touched
• Only one feature/fix was added per PR and the code change compiles without warnings
• The code change is tested and works with Tasmota core ESP8266 V.2.7.8
• The code change is tested and works with Tasmota core ESP32 V.3.1.10
• I accept the CLA.

NOTE: The code change must pass CI tests. Your PR cannot be merged unless tests pass