patch 8.2.1664: memory leak when using :mkview with a terminal buffer

Problem:    Memory leak when using :mkview with a terminal buffer.
Solution:   Don't use a hastab for :mkview. (Rob Pilling, closes #6935)
diff --git a/src/terminal.c b/src/terminal.c
index e2fcf40..2043c84 100644
--- a/src/terminal.c
+++ b/src/terminal.c
@@ -940,7 +940,7 @@
     const int	bufnr = wp->w_buffer->b_fnum;
     term_T	*term = wp->w_buffer->b_term;
 
-    if (wp->w_buffer->b_nwindows > 1)
+    if (terminal_bufs != NULL && wp->w_buffer->b_nwindows > 1)
     {
 	// There are multiple views into this terminal buffer. We don't want to
 	// create the terminal multiple times. If it's the first time, create,
@@ -978,7 +978,7 @@
     if (fprintf(fd, "let s:term_buf_%d = bufnr()", bufnr) < 0)
 	return FAIL;
 
-    if (wp->w_buffer->b_nwindows > 1)
+    if (terminal_bufs != NULL && wp->w_buffer->b_nwindows > 1)
     {
 	char *hash_key = alloc(NUMBUFLEN);