Fixed minor compile error

src/LogCompressor.cc

@@ -83,7 +83,7 @@ void LogCompressor::run()
 
 	// Now update each key with its index in the output string. These are
 	// all offset by one to account for the first field: timestamp_ms.
-	QMap<QString, int>::iterator i = messageMap.constBegin();
+    QMap<QString, int>::iterator i = messageMap.begin();
 	int j;
 	for (i = messageMap.begin(), j = 1; i != messageMap.end(); ++i, ++j) {
 		i.value() = j;
@@ -174,4 +174,4 @@ bool LogCompressor::isFinished()
 int LogCompressor::getCurrentLine()
 {
 	return currentDataLine;
-}
\ No newline at end of file
+}