fmbtgti: fix OCR text finding with empty string
fmbtgti: fix OCR text finding with empty string

Finding empty OCR text with match == 0.0 returns every OCR string,
empty string with match != 0.0 returns empty list.

01org/fMBT,acozzette/fMBT,pombreda/fMBT,giantpinkwalrus/fMBT,pombreda/fMBT,violep01/fMBT,pombreda/fMBT,yoonkiss/fMBT,rseymour/fMBT,heivi/fMBT,pombreda/fMBT,mixu-/fMBT,01org/fMBT,giantpinkwalrus/fMBT,acozzette/fMBT,mlq/fMBT,mixu-/fMBT,yoonkiss/fMBT,yoonkiss/fMBT,yoonkiss/fMBT,01org/fMBT,01org/fMBT,acozzette/fMBT,giantpinkwalrus/fMBT,mlq/fMBT,violep01/fMBT,01org/fMBT,giantpinkwalrus/fMBT,mixu-/fMBT,rseymour/fMBT,heivi/fMBT,violep01/fMBT,acozzette/fMBT,mixu-/fMBT,mlq/fMBT,rseymour/fMBT,heivi/fMBT,yoonkiss/fMBT,heivi/fMBT,rseymour/fMBT,mlq/fMBT,mlq/fMBT,heivi/fMBT,giantpinkwalrus/fMBT,heivi/fMBT,pombreda/fMBT,heivi/fMBT,rseymour/fMBT,mlq/fMBT,violep01/fMBT,rseymour/fMBT,pombreda/fMBT,pombreda/fMBT,rseymour/fMBT,mixu-/fMBT,mlq/fMBT,violep01/fMBT,acozzette/fMBT