Hoping to avoid a crash in OSX for a problem blitzrage found

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@89051 65c4cc65-6c06-0410-ace0-fbb531ad65f3

main/ast_expr2.fl

@@ -264,12 +264,16 @@ int ast_expr(char *expr, char *buf, int length, struct ast_channel *chan)
 			res_length = snprintf(buf, length, FP___PRINTF, io.val->u.i);
 			return_value = (res_length <= length) ? res_length : length;
 		} else {
+			if (io.val->u.s)
 #if defined(STANDALONE) || defined(LOW_MEMORY) || defined(STANDALONE_AEL)
 				strncpy(buf, io.val->u.s, length - 1);
 #else /* !STANDALONE && !LOW_MEMORY */
 				ast_copy_string(buf, io.val->u.s, length);
 #endif /* STANDALONE || LOW_MEMORY */
+			else
+				buf[0] = 0;
 			return_value = strlen(buf);
+			if (io.val->u.s)
 				free(io.val->u.s);
 		}
 		free(io.val);

main/ast_expr2f.c

@@ -3207,12 +3207,16 @@ int ast_expr(char *expr, char *buf, int length, struct ast_channel *chan)
 			res_length = snprintf(buf, length, FP___PRINTF, io.val->u.i);
 			return_value = (res_length <= length) ? res_length : length;
 		} else {
+			if (io.val->u.s)
 #if defined(STANDALONE) || defined(LOW_MEMORY) || defined(STANDALONE_AEL)
 				strncpy(buf, io.val->u.s, length - 1);
 #else /* !STANDALONE && !LOW_MEMORY */
 				ast_copy_string(buf, io.val->u.s, length);
 #endif /* STANDALONE || LOW_MEMORY */
+			else
+				buf[0] = 0;
 			return_value = strlen(buf);
+			if (io.val->u.s)
 				free(io.val->u.s);
 		}
 		free(io.val);