 Image conversion crash fix (#501)
 Image conversion crash fix (#501)

* b/161683278

This PR fixes the crash caused by the bug. And also
     - Prints more information when image conversion is failed
     - Renames the function that reads min and max value from Float src
google/agi,google/agi,google/agi,google/agi,google/agi,google/agi,google/agi,google/agi