add a special value to update threshold spinbox (follows e09683b1)
Prevent crash in case of invalid geometries
fix gdaltools merge, tileindex and info
fix GdalTools warp
fix GdalTools assign and extract projection
fix GdalTools contour
Fixes #8065
also handle ringless polygons with GEOS <3.3 (follows 6370153e)
Merge pull request #659 from slarosa/fix_8065

[DB Manager] Fixes #8065
Fix crash when creating/loading projects. Fixes #7931
fix a iteration
Update CRS cache when deleting a custom CRS
Merge pull request #660 from minorua/grad_it

fix a iteration
Som fTools fixes for SIP API updates
Improved implementation
[ftools] Fix "Join attributes by location"
Fix memory leak in QgsFeature sip api
Fix memory leak in ogr provider
Fix python console for Python 2.6
[ftools] Further SIP API updates