menuselect/menuselect_curses: Resolves sprintf usage error

Acccording to the man page for sprintf, using the same buffer for
output as one used as an input yields undefined behavior.
This patch should work around this problem.

ASTERISK-27903
Reported-by: Alexander Traud

Change-Id: I2213dcb454aff26457e2e4cc9c6821276463ae3a

menuselect/menuselect_curses.c

@@ -227,7 +227,7 @@ static void display_mem_info(WINDOW *menu, struct member *mem, int start_y, int
 				buf[0] = '\0';
 				new_line = 1;
 			}
-			sprintf(buf, "%s%*.*s%s", buf, new_line ? 0 : 1, new_line ? 0 : 1, " ", word);
+			sprintf(buf + strlen(buf), "%*.*s%s", new_line ? 0 : 1, new_line ? 0 : 1, " ", word);
 			new_line = 0;
 		}
 		if (strlen(buf)) {