osmux: osmux_snprintf(): Remove dangling whitespace at the end of dummy frames

Change-Id: I1ef73807c3300cbcc332f32e6bb905d9b30557be

src/osmux.c

@@ -1126,6 +1126,8 @@ int osmux_snprintf(char *buf, size_t size, struct msgb *msg)
 			}
 
 			if (osmuxh->ft == OSMUX_FT_VOICE_AMR) {
+				ret = snprintf(buf + offset, remain, " ");
+				SNPRINTF_BUFFER_SIZE(ret, remain, offset);
 				ret = osmux_snprintf_payload(buf + offset, remain,
 							     osmux_get_payload(osmuxh),
 							     payload_len);