If calling Stop Coverage for a page where Start Coverage is not called, logging of the keyword is wrong

[aaltat]

Describe the bug
If calling Stop Coverage for a page where Start Coverage is not called, logging of the keyword is wrong. In this case Stop Coverage keyword says that report creation was successful, even the report was not created. Instead keyword should log that report was not created, because coverage collection was not starter

To Reproduce

*** Settings ***
Library    Browser

*** Test Cases ***
Example
    New Page    http://www.google.com
    Stop Coverage

Expected behavior
Stop Coverage should say that report was not created because Start Coverage was not called for the currently active page.