patch 9.0.0069: leaking memory when using text prop with inserted text

Problem:    Leaking memory when using text prop with inserted text.
Solution:   Clear the growarray with text.
diff --git a/src/buffer.c b/src/buffer.c
index bbbfdb7..436c0e9 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -1004,6 +1004,9 @@
 #ifdef FEAT_NETBEANS_INTG
     netbeans_file_killed(buf);
 #endif
+#ifdef FEAT_PROP_POPUP
+    ga_clear_strings(&buf->b_textprop_text);
+#endif
     map_clear_mode(buf, MAP_ALL_MODES, TRUE, FALSE);  // clear local mappings
     map_clear_mode(buf, MAP_ALL_MODES, TRUE, TRUE);   // clear local abbrevs
     VIM_CLEAR(buf->b_start_fenc);