patch 8.2.4185: cannot use an import in 'indentexpr'

Problem:    Cannot use an import in 'indentexpr'.
Solution:   Set the script context when evaluating 'indentexpr'
diff --git a/src/indent.c b/src/indent.c
index a1012d2..8dd4ef9 100644
--- a/src/indent.c
+++ b/src/indent.c
@@ -1829,6 +1829,7 @@
     int		save_State;
     int		use_sandbox = was_set_insecurely((char_u *)"indentexpr",
 								   OPT_LOCAL);
+    sctx_T	save_sctx = current_sctx;
 
     // Save and restore cursor position and curswant, in case it was changed
     // via :normal commands
@@ -1839,6 +1840,7 @@
     if (use_sandbox)
 	++sandbox;
     ++textwinlock;
+    current_sctx = curbuf->b_p_script_ctx[BV_INDE];
 
     // Need to make a copy, the 'indentexpr' option could be changed while
     // evaluating it.
@@ -1852,6 +1854,7 @@
     if (use_sandbox)
 	--sandbox;
     --textwinlock;
+    current_sctx = save_sctx;
 
     // Restore the cursor position so that 'indentexpr' doesn't need to.
     // Pretend to be in Insert mode, allow cursor past end of line for "o"