lib.log.log(): Fix early return without flags set

When position, prio, and date are all absent from the log flags, the
msg variable is empty. The early return 'if not len(msg): return'
would then skip printing the actual message in margs.

Fix by checking both msg and margs before returning. This ensures
messages are still printed even when no prefix flags are set.

Signed-off-by: Jan Lindemann <jan@janware.com>

src/python/jw/pkg/lib/log.py

@@ -240,7 +240,7 @@ def log(  # export
 
     msg += _log_prefix
 
-    if not len(msg):
+    if not len(msg) and not len(margs):
         return
 
     if len(margs):