Fixed void unwanted OTA upgrade when safeboot starts for the first time

[s-hadinger]

Description:

When booting the first time on safeboot partition, an unwanted OTA upgrade from OtaURL would automatically be triggered. This is due to NvmLoad("otal", "otal", &pOtaLoader, sizeof(pOtaLoader)); not updating pOtaLoader since the value does not yet exist in NMV, hence the value would default to a random value from the stack, and generally not 0.

This PR sets the default value to 0 so no unwanted OTA is done when NVM is not yet populated.

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.2.7.6
• The code change is tested and works with Tasmota core ESP32 V.3.0.0
• I accept the CLA.

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