Automatic merge from submit-queue

avoid repeated length calculation and some other code improvements

**What this PR does / why we need it**:
1. in function `ParsePairs`,  calculating `invalidBuf`'s length over and over again brings performance penalty. a `invalidBufNonEmpty` bool value can fix this.
2. pairArg is not a string template and also there is no other arguments for `fmt.Sprintf`, so i remove `fmt.Sprintf`
3. in function `DumpReaderToFile`, we must check nil error first before defer statement, otherwise there maybe a potential nil error on `f.Close()`
4. add nil checks into `GetWideFlag` function
5. some other minor code improvements for better readability.
Signed-off-by: bruceauyeung <ouyang.qinhua@zte.com.cn>