patch 8.2.2165: Vim9: assignment to dict member does not work

Problem:    Vim9: assignment to dict member does not work.
Solution:   Fix recognizing dict member. (closes #7484)
diff --git a/src/ex_docmd.c b/src/ex_docmd.c
index 152eda6..95d4dd1 100644
--- a/src/ex_docmd.c
+++ b/src/ex_docmd.c
@@ -3332,6 +3332,8 @@
 
 		// When followed by "=" or "+=" then it is an assignment.
 		++emsg_silent;
+		if (*after == '.')
+		    after = skipwhite(after + 1);
 		if (skip_expr(&after, NULL) == OK)
 		    after = skipwhite(after);
 		else