common/ompio: fix division by zero problem with empty fview

When using an empty fileview, a division by zero bug can occur in ompio. Not entirely sure why the problem did not show up previously, but some recent changes trigger that bug in one of our tests.

This pr is part of a fix applied in commit f6b3a0a

Fixes Issue #6703

Signed-off-by: Edgar Gabriel <egabriel@central.uh.edu>

ompi/mca/common/ompio/common_ompio_file_open.c

@@ -9,7 +9,7 @@
  *                         University of Stuttgart.  All rights reserved.
  * Copyright (c) 2004-2005 The Regents of the University of California.
  *                         All rights reserved.
- * Copyright (c) 2008-2018 University of Houston. All rights reserved.
+ * Copyright (c) 2008-2019 University of Houston. All rights reserved.
  * Copyright (c) 2015-2018 Research Organization for Information Science
  *                         and Technology (RIST). All rights reserved.
  * Copyright (c) 2016      Cisco Systems, Inc.  All rights reserved.
@@ -384,6 +384,13 @@ int mca_common_ompio_file_get_position (ompio_file_t *fh,
 {
     OMPI_MPI_OFFSET_TYPE off;
 
+    if ( 0 == fh->f_view_extent ||
+         0 == fh->f_view_size   ||
+         0 == fh->f_etype_size ) {
+        *offset = 0;
+        return OMPI_SUCCESS;
+    }
+    
     /* No. of copies of the entire file view */
     off = (fh->f_offset - fh->f_disp)/fh->f_view_extent;