Disable channel icon scan when icon path is empty

XBMC checks the icon path and terminates the scan early if no path is set. This commit causes the setting to respect that.
RssReader::Process: fix: read unknown length files correctly
ScraperUrl::Get: fix: avoid race conditions
Merge pull request #3514 from Karlson2k/scraperurl_fix_01

ScraperUrl::Get: fix: avoid race conditions
Fix a warning on windows.
Fix Player.play crash on Windows due to trying to assign NULL to a reference.
Merge pull request #3513 from Karlson2k/rss_reader_fix_01

RssReader::Process: fix: read files with unknown length correctly
fix compile warning (assignment inside if)
fix HasExtension didn't necessarily terminate correctly
[osx] - fix windowed/fullscreen transitions with multi screen setups
fix - deadlock on timing of setting the ending status of the PythonInvoker.
fix - clash with StdString's use of the TRACE macro.
[xcode] - remove stale references to ios6.1 sdk
Merge pull request #3516 from Memphiz/osxmultiscreen

[osx] - fix windowed/fullscreen transitions with multi screen setups
Merge pull request #3392 from garbear/pvrmenu.searchicons

Disable channel icon scan when icon path is empty
Merge pull request #3506 from jmarshallnz/compile_warnings

Compile warnings
[AE] refactor audio settings page
dvdplayer: adapt to changes in audio settings
paplayer: adapt to changes in audio settings
GUIDialogAudioSettings: adapt to changes in audio settings