Contextbrowser: Remove 'separated by only whitespace' possibility for showing the problem tooltip

In my opinion, it is undesirable to show the problem tooltip in unexpected situations where it might get into the user's way. Thus, I am proposing here to remove the code that shows the problem tooltip if there is only whitespace between the cursor and the problem, as this seems like a somewhat random criterion to me. After this, the problem tooltip should only be shown if the problem is actually on the same line as the cursor (where the user will more likely expect the tooltip to show up).