Prevent test failure and possible data loss due to API change in libical 3.0.7.

https://gitlab.gnome.org/GNOME/evolution-data-server/issues/185
https://lists.infradead.org/pipermail/libical-devel/2020-January/000907.html

Adapted from upstream:

https://gitlab.gnome.org/GNOME/evolution-data-server/commit/77384ab552c19bf374dbeda53dc37f98d07bd4ec

diff --git a/CMakeLists.txt b/CMakeLists.txt
index e16b8b225..b3c881967 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -111,7 +111,7 @@ add_definitions(-DSOUP_VERSION_MIN_REQUIRED=${soup_encoded_version})
 
 set(gcr_minimum_version 3.4)
 set(libgdata_minimum_version 0.15.1)
-set(libical_glib_minimum_version 3.0.5)
+set(libical_glib_minimum_version 3.0.7)
 set(libsecret_minimum_version 0.5)
 set(libxml_minimum_version 2.0.0)
 set(sqlite_minimum_version 3.7.17)
diff --git a/src/calendar/libedata-cal/e-cal-meta-backend.c b/src/calendar/libedata-cal/e-cal-meta-backend.c
index 7501f2a43..93f4806ba 100644
--- a/src/calendar/libedata-cal/e-cal-meta-backend.c
+++ b/src/calendar/libedata-cal/e-cal-meta-backend.c
@@ -4067,8 +4067,7 @@ e_cal_meta_backend_inline_local_attachments_sync (ECalMetaBackend *meta_backend,
 					gchar *base64;
 
 					base64 = g_base64_encode ((const guchar *) content, len);
-					new_attach = i_cal_attach_new_from_data (base64, NULL, NULL);
+					new_attach = i_cal_attach_new_from_data (base64, (GFunc) g_free, NULL);
 					g_free (content);
-					g_free (base64);
 
 					ecmb_remove_all_but_filename_parameter (prop);