We don't need to attempt to read in an XML log file using {{{-[NSString stringWithCon...

We don't need to attempt to read in an XML log file using {{{-[NSString stringWithContentsOfFile:}}} -- the return value is wholly ignored, and it returns nil in many situations when reading in UTF8 files if the system was loaded in a non-ASCII-character-set language such as Chinese.  Removing this fixes display of XML logs on such systems and also makes display of XML logs more efficient on all systems, cutting the number of times the file is read to display in half (to 1 time instead of 2).  Fixes #5026

git-svn-id: svn://svn.adiumx.com/adium/trunk@17789 1c916fce-81e2-0310-a464-8ca513f45935