improve error handling: String instead of numbers

[thanatos11]

Issue description
When the pins or other elements on map are presented with strings instead of number, the elements or pins do not show on the map, there is no feedback in console, no error.

Steps to reproduce and a minimal demo of the problem

made a pin and served latitude and longitude coordinates in string format. That pin is not rendered.

Expected/desired behavior

Whould be great if an error would show in console. Even better if in converts it to number and displays a warning.

[sebholstein]

@thanatos11 I agree, this can be a really annoying thing. (No errors, no marker). We should try to convert the value if it's a string.