JPEG: Fix regression when handling files with EOF error

[lastzero]

Due to changes in our JPEG image library, the error message for files with EOF errors has changed, so that e.g. panoramas taken with a Samsung S21 could not be indexed anymore:

• JPEG: Support panoramas taken with a Samsung S21 #3363

[lastzero]

We now check if "EOF" is contained anywhere in the error message, not just at the beginning. Unless the error changes completely in future library versions, this should prevent further regressions. An updated preview build will be available for testing soon!