Fixed wrong ISO speed shown in some Canon cr2 files
Added null check in setScale
Fixed metadata disappearing issue
Merge pull request #93 from ktgw0316/issue87

Fixed NPE while zooming with mouse wheel (#87)
Merge pull request #92 from ktgw0316/issue34

Fixed wrong ISO speed shown in some Canon cr2 files (#34)
Merge pull request #91 from ktgw0316/issue76

Fixed metadata disappearing issue (#76)