libobs: Add validity checks for obs objects

These functions are intended to log a warning when an obs function is
called with a null object.

libobs/obs-internal.h

@@ -48,6 +48,40 @@ struct draw_callback {
 	void *param;
 };
 
+/* ------------------------------------------------------------------------- */
+/* validity checks */
+
+static inline bool obs_object_valid(const void *obj, const char *f,
+		const char *t)
+{
+	if (!obj) {
+		blog(LOG_WARNING, "Null %s passed to %s!", t, f);
+		return false;
+	}
+
+	return true;
+}
+
+static inline bool obs_source_valid(const obs_source_t *obj, const char *f)
+{
+	return obs_object_valid(obj, f, "source");
+}
+
+static inline bool obs_output_valid(const obs_output_t *obj, const char *f)
+{
+	return obs_object_valid(obj, f, "output");
+}
+
+static inline bool obs_encoder_valid(const obs_encoder_t *obj, const char *f)
+{
+	return obs_object_valid(obj, f, "encoder");
+}
+
+static inline bool obs_service_valid(const obs_service_t *obj, const char *f)
+{
+	return obs_object_valid(obj, f, "service");
+}
+
 /* ------------------------------------------------------------------------- */
 /* modules */