Made few changes to TCGenerator.java

The previous version of TCGenerator.java only calls the getErrorMsgs()
method in Idf.java to retrieve error messages. However, since the
current version of Idf.java now throws IdfFormatException for every
anomaly in an IDF, then TCGenerator must be made to catch these
exceptions and write them to the log file. This change has been effected
in TCGenerator.java.