patch 8.2.4358: Vim9: line number of exception is not set

Problem:    Vim9: line number of exception is not set.
Solution:   Set the line number before throwing an exception. (closes #9755)
diff --git a/src/vim9execute.c b/src/vim9execute.c
index 1412d08..f6456d6 100644
--- a/src/vim9execute.c
+++ b/src/vim9execute.c
@@ -3826,6 +3826,7 @@
 			}
 		    }
 
+		    SOURCING_LNUM = iptr->isn_lnum;
 		    if (throw_exception(tv->vval.v_string, ET_USER, NULL)
 								       == FAIL)
 		    {