patch 8.2.3585: crash when passing float to "term_rows" of term_start()

Problem:    Crash when passing float to "term_rows" in the options argument of
            term_start(). (Virginia Senioria)
Solution:   Bail out if the argument is not a number. (closes #9116)
diff --git a/src/testdir/test_terminal.vim b/src/testdir/test_terminal.vim
index eb5924a..3e263ef 100644
--- a/src/testdir/test_terminal.vim
+++ b/src/testdir/test_terminal.vim
@@ -467,6 +467,10 @@
   bwipe!
   call assert_equal([7, 27], size)
 
+  if has('float')
+    call assert_fails("call term_start(cmd, {'term_rows': 10.0})", 'E805:')
+  endif
+
   call delete('Xtext')
 endfunc