gbproxy: Fix issues found by Coverity

gbproxy_patch_bssgp: Move a check for tlli_info in front of the first
conditional that depends on it, and return immediately if it is NULL.

gbproxy_register_tlli: Initialize tlli_already_known to 0.

Fixes: Coverity CID 1232691
Fixes: Coverity CID 1232692
Sponsored-by: On-Waves ehf

openbsc/src/gprs/gb_proxy_patch.c

@@ -335,7 +335,10 @@ void gbproxy_patch_bssgp(struct msgb *msg, uint8_t *bssgp, size_t bssgp_len,
 		goto patch_error;
 	}
 
-	if (parse_ctx->tlli_enc && tlli_info) {
+	if (!tlli_info)
+		return;
+
+	if (parse_ctx->tlli_enc) {
 		uint32_t tlli = gbproxy_map_tlli(parse_ctx->tlli,
 						 tlli_info, parse_ctx->to_bss);
 

openbsc/src/gprs/gb_proxy_tlli.c

@@ -309,7 +309,7 @@ struct gbproxy_tlli_info *gbproxy_register_tlli(
 {
 	struct gbproxy_tlli_info *tlli_info;
 	int enable_patching = -1;
-	int tlli_already_known;
+	int tlli_already_known = 0;
 
 	/* Check, whether the IMSI matches */
 	if (gprs_is_mi_imsi(imsi, imsi_len)) {