Modifies exposure and ISO number metadata fetching functions to check their results for sanity. Closes #2140.
Modifies exposure and ISO number metadata fetching functions to check their results for sanity. Closes #2140.


jof/shotwell,ritchiewilson/shotwell,ritchiewilson/shotwell,jof/shotwell,jimbonator/shotwell,jimbonator/shotwell,h4ck3rm1k3/shotwell,polymeris/shotwell,Sanva/shotwell-gsoc,ritchiewilson/shotwell,h4ck3rm1k3/shotwell,jof/shotwell,jimbonator/shotwell,h4ck3rm1k3/shotwell,damianmoore/shotwell,damianmoore/shotwell,damianmoore/shotwell,polymeris/shotwell,Sanva/shotwell-gsoc,abrauchli/shotwell,abrauchli/shotwell,polymeris/shotwell,Sanva/shotwell-gsoc,abrauchli/shotwell