check for valid progress function

This commit was SVN r1468.

src/mca/pml/teg/src/pml_teg_progress.c

@@ -10,8 +10,11 @@ int mca_pml_teg_progress(void)
     /*
      * Progress each of the PTL modules
      */
-    for(i=0; i<mca_pml_teg.teg_num_ptl_modules; i++)
-        mca_pml_teg.teg_ptl_modules[i]->ptlm_progress(tstamp);
+    for(i=0; i<mca_pml_teg.teg_num_ptl_modules; i++) {
+        mca_ptl_base_module_progress_fn_t progress = mca_pml_teg.teg_ptl_modules[i]->ptlm_progress;
+        if(NULL != progress)
+            progress(tstamp);
+    }
     return OMPI_SUCCESS;
 }