also recalculate layer extent after rollback (fixes #3155)

src/core/qgsvectorlayer.cpp

@@ -2310,6 +2310,10 @@ bool QgsVectorLayer::rollBack( bool deleteBuffer )
     return false;
   }
 
+  bool rollbackExtent = !mEditBuffer->mDeletedFeatureIds.isEmpty() ||
+                        !mEditBuffer->mAddedFeatures.isEmpty() ||
+                        !mEditBuffer->mChangedGeometries.isEmpty();
+
   emit beforeRollBack();
 
   mEditBuffer->rollBack();
@@ -2336,6 +2340,9 @@ bool QgsVectorLayer::rollBack( bool deleteBuffer )
     mCache->deleteCachedGeometries();
   }
 
+  if ( rollbackExtent )
+    updateExtents();
+
   emit repaintRequested();
   return true;
 }