OPENNLP-1781: SentenceDetectorME throws StringIndexOutOfBoundsException when sentence starts with an abbreviation

[rzo1]

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Note:

When an abbreviation appears at the beginning of a sentence, OpenNLP 2.5.6's SentenceDetectorME can throw a java.lang.StringIndexOutOfBoundsException.

This is a regression from https://issues.apache.org/jira/browse/OPENNLP-1767