update math submodule to 7f4e3a4af5

yiz · yiz · commit b69492ba98ef · 2019-12-18T14:24:34.000-08:00
diff --git a/lib/stan_math b/lib/stan_math
@@ -1 +1 @@
-Subproject commit 025a142ec01b68e91adf339a9b86d67e6d0e20ee
+Subproject commit 7f4e3a4af56d8471606b414ed59364898638b323
