Fix double free issue in qemu_set_log_filename().

After freeing the logfilename, we set logfilename to NULL, in case of an
error which returns without setting logfilename.

Signed-off-by: Robert Foley <robert.foley@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20191118211528.3221-2-robert.foley@linaro.org>

util/log.c

@@ -113,6 +113,7 @@ void qemu_set_log_filename(const char *filename, Error **errp)
 {
     char *pidstr;
     g_free(logfilename);
+    logfilename = NULL;
 
     pidstr = strstr(filename, "%");
     if (pidstr) {