Avoid references to disassociated POINTERs in examples

examples/example.f90

@@ -166,7 +166,11 @@ CONTAINS
     CALL deallocateTimedelta(mtime_td)
 
     mtime_td => newTimedelta("PT7536.0003S")
-    CALL timedeltatostring(mtime_td, td_string)
+    IF (ASSOCIATED(mtime_td)) THEN
+      CALL timedeltatostring(mtime_td, td_string)
+    ELSE
+      td_string = "<null>"
+    END IF
     WRITE (0, *) "PT7536.0003S (expect <null>) = ", TRIM(td_string)
     CALL deallocateTimedelta(mtime_td)
 

examples/repetitor.f90

@@ -56,7 +56,11 @@ CONTAINS
     IF (lstart) THEN
       PRINT *, 'Start: ', TRIM(start)
       s => newDateTime(start)
-      CALL datetimeToString(s, dstring)
+      IF (ASSOCIATED(s)) THEN
+        CALL datetimeToString(s, dstring)
+      ELSE
+        dstring = "<null>"
+      END IF
       PRINT *, 'Start rev: ', TRIM(dstring)
       CALL deallocateDateTime(s)
     END IF