Fix M_PathParts instead

src/m_misc.c

@@ -2457,6 +2457,8 @@ int M_PathParts(const char *path)
 	int n;
 	const char *p;
 	const char *t;
+	if (path == NULL)
+		return 0;
 	for (n = 0, p = path ;; ++n)
 	{
 		t = p;

src/sdl/i_main.c

@@ -197,12 +197,9 @@ int main(int argc, char **argv)
 					format, timeinfo);
 		}
 
-		if (logdir)
-		{
-			M_MkdirEachUntil(logfilename,
-					M_PathParts(logdir) - 1,
-					M_PathParts(logfilename) - 1, 0755);
-		}
+		M_MkdirEachUntil(logfilename,
+				M_PathParts(logdir) - 1,
+				M_PathParts(logfilename) - 1, 0755);
 
 #ifdef __unix__
 		logstream = fopen(logfilename, "w");