Fix coverity warnings

src/civetweb.c

@@ -12259,7 +12259,7 @@ refresh_trust(struct mg_connection *conn)
 	if (chain == NULL) {
 		chain = pem;
 	}
-	if (*chain == 0) {
+	if ((chain != NULL) && (*chain == 0)) {
 		chain = NULL;
 	}
 

src/handle_form.inl

@@ -545,10 +545,17 @@ mg_handle_form_request(struct mg_connection *conn,
 		if (boundary[0] == '"') {
 			/* RFC 2046 permits the boundary string to be quoted. */
 			hbuf = strchr(boundary + 1, '"');
+			if (!hbuf) {
+				/* Malformed request */
+				return -1;
+			}
 			if (*hbuf) {
 				*hbuf = 0;
 				boundary++;
 				bl = strlen(boundary);
+			} else {
+				/* Malformed request */
+				return -1;
 			}
 		}