i.segment: fix -w flag

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@57074 15284696-431f-4ddb-bdfa-cd5b030d7da7

imagery/i.segment/open_files.c

@@ -61,6 +61,7 @@ int open_files(struct globals *globals)
     /* Get min/max values of each input raster for scaling */
 
     globals->max_diff = 0.;
+    globals->nbands = Ref.nfiles;
 
     for (n = 0; n < Ref.nfiles; n++) {
 	/* returns -1 on error, 2 on empty range, quiting either way. */
@@ -86,8 +87,6 @@ int open_files(struct globals *globals)
     /* ********** find out file segmentation size ************ */
     G_debug(1, "Calculate temp file sizes...");
 
-    globals->nbands = Ref.nfiles;
-
     /* size of each element to be stored */
 
     inlen = sizeof(DCELL) * Ref.nfiles;