media: Log and fail gracefully on invalid EXIF coordinates

media: Log and fail gracefully on invalid EXIF coordinates

The $coord value is a value extracted from the EXIF section of an
image file. We expect it to be a float, but there is no guarantee this
is the case. It could, for example, be an empty string.

I suggest this trivial fix. It does have the following effects:
* Instead of logging a PHP notice when floor() hits something that is
  not a number, I try to log something that's more useful for later,
  more in-depth debugging. Note this log call isn't necessarily meant
  to stay, but to find an even better fix for this issue.
* I return the string as it is. If it's "foo", the user will see "foo"
  instead of "0° 0′ 0″ N", which wasn't helpful.

Also note how wrong and misleading the PHPDoc block for this function
was.

Bug: T226751
Change-Id: I1ca98728de4113ee1ae4362bd3e62b425d589388
(cherry picked from commit f6787ede2db29fcc2c1923e23eaa2e9bf86522a1)