Another minor warning about casting a double into a float

tests/test-mserial-bin.c

@@ -102,7 +102,7 @@ static void test_out_fill(void)
 
   el2->activated = true;
   el2->data->vala = 145788;
-  el2->data->valb = -0.1;
+  el2->data->valb = -0.1f;
   el2->data->valc = false;
   string_set_str(el2->data->vald, "This is a string test.");
   a2_push_back(el2->data->vale, 1);