Fix possible use of uninitialized variable during error handling in mysql.cc

client/mysql.cc:
  In com_go(): Initialize 'warnings' count, in case an error occurs before
  it is properly set.

client/mysql.cc

@@ -2155,7 +2155,8 @@ com_go(String *buffer,char *line __attribute__((unused)))
 {
   char		buff[200], time_buff[32], *pos;
   MYSQL_RES	*result;
-  ulong		timer, warnings;
+  ulong		timer;
+  ulong         warnings= 0;
   uint		error= 0;
   int           err= 0;