patch 8.1.1819: :pedit does not work with a popup preview window

Problem:    :pedit does not work with a popup preview window.
Solution:   Avoid aborting with an error. (fixes #4777)  Also double check
            that after prepare_tagpreview() the current window is not a
            popup window.
diff --git a/src/testdir/dumps/Test_popupwin_previewpopup_6.dump b/src/testdir/dumps/Test_popupwin_previewpopup_6.dump
new file mode 100644
index 0000000..cd160d3
--- /dev/null
+++ b/src/testdir/dumps/Test_popupwin_previewpopup_6.dump
@@ -0,0 +1,14 @@
+|o+0&#ffffff0|n|e| @71
+|#|i|n|c|l|u|d|e| |"|X|h|e|a|d|e|r|.|h|"| @54
+|t|h|r|e@1| @69
+|f|o|u|r| @70
+|f|i|v|e| @70
+|s|i|x| @71
+|s|e|v|e|n| @69
+|f|i|n|d| |t|h|e|w|o|r|d| |s|o|m|e|w|h|e|r|e| @52
+|n|i|n|e| @70
+|t|h|i|s| |i|s| |a|n|o|t|h|e|r| |w|o|r|d| @54
+|v|e|r|y| |l|o|n|g| |l|i|n|e| |w|h|e|r|e| |t|h|e| |w|o|r|d| |i|s| |a|l|s|o| >a|n|o|t|h|e|r| @29
+|~+0#4040ff13&| @73
+|~| @73
+|:+0#0000000&|p|c|l|o|s|e| @49|1@1|,|3|9| @8|A|l@1| 
diff --git a/src/testdir/dumps/Test_popupwin_previewpopup_7.dump b/src/testdir/dumps/Test_popupwin_previewpopup_7.dump
new file mode 100644
index 0000000..f510b8b
--- /dev/null
+++ b/src/testdir/dumps/Test_popupwin_previewpopup_7.dump
@@ -0,0 +1,14 @@
+|o+0&#ffffff0|n|e| @71
+|#|i|n|c|l|u|d|e| |"|X|h|e|a|d|e|r|.|h|"| @54
+|t|h|r|e@1| @69
+|f|o|u|r| @70
+|f|i|v|e| @27|╔+0#0000001#ffd7ff255| |X|t|a|g|f|i|l|e| |═@30|X
+|s+0#0000000#ffffff0|i|x| @28|║+0#0000001#ffd7ff255|2|0| @37| +0#0000000#a8a8a8255|║+0#0000001#ffd7ff255
+|s+0#0000000#ffffff0|e|v|e|n| @26|║+0#0000001#ffd7ff255|t|h|e|w|o|r|d| |i|s| |h|e|r|e| @24| +0#0000000#a8a8a8255|║+0#0000001#ffd7ff255
+|f+0#0000000#ffffff0|i|n|d| |t|h|e|w|o|r|d| |s|o|m|e|w|h|e|r|e| @9|║+0#0000001#ffd7ff255|2@1| @37| +0#0000000#0000001|║+0#0000001#ffd7ff255
+|n+0#0000000#ffffff0|i|n|e| @27|║+0#0000001#ffd7ff255|2|3| @37| +0#0000000#a8a8a8255|║+0#0000001#ffd7ff255
+|t+0#0000000#ffffff0|h|i|s| |i|s| |a|n|o|t|h|e|r| |w|o|r|d| @11|╚+0#0000001#ffd7ff255|═@40|⇲
+|v+0#0000000#ffffff0|e|r|y| |l|o|n|g| |l|i|n|e| |w|h|e|r|e| |t|h|e| |w|o|r|d| |i|s| |a|l|s|o| >a|n|o|t|h|e|r| @29
+|~+0#4040ff13&| @73
+|~| @73
+|:+0#0000000&| @55|1@1|,|3|9| @8|A|l@1| 
diff --git a/src/testdir/dumps/Test_popupwin_previewpopup_8.dump b/src/testdir/dumps/Test_popupwin_previewpopup_8.dump
new file mode 100644
index 0000000..6e88fff
--- /dev/null
+++ b/src/testdir/dumps/Test_popupwin_previewpopup_8.dump
@@ -0,0 +1,14 @@
+|o+0&#ffffff0|n|e| @71
+|#|i|n|c|l|u|d|e| |"|X|h|e|a|d|e|r|.|h|"| @54
+|t|h|r|e@1| @69
+|f|o|u|r| @70
+|f|i|v|e| @27|╔+0#0000001#ffd7ff255| |X|h|e|a|d|e|r|.|h| |═@29|X
+|s+0#0000000#ffffff0|i|x| @28|║+0#0000001#ffd7ff255|1+0#e000002&|0| +0#0000001&@37| +0#0000000#a8a8a8255|║+0#0000001#ffd7ff255
+|s+0#0000000#ffffff0|e|v|e|n| @26|║+0#0000001#ffd7ff255|s|e|a|r|c|h|e|d| |w|o|r|d| |i|s| |h|e|r|e| @18| +0#0000000#a8a8a8255|║+0#0000001#ffd7ff255
+|f+0#0000000#ffffff0|i|n|d| |t|h|e|w|o|r|d| |s|o|m|e|w|h|e|r|e| @9|║+0#0000001#ffd7ff255|1+0#e000002&|2| +0#0000001&@37| +0#0000000#0000001|║+0#0000001#ffd7ff255
+|n+0#0000000#ffffff0|i|n|e| @27|║+0#0000001#ffd7ff255|1+0#e000002&|3| +0#0000001&@37| +0#0000000#a8a8a8255|║+0#0000001#ffd7ff255
+|t+0#0000000#ffffff0|h|i|s| |i|s| |a|n|o|t|h|e|r| |w|o|r|d| @11|╚+0#0000001#ffd7ff255|═@40|⇲
+|v+0#0000000#ffffff0|e|r|y| |l|o|n|g| |l|i|n|e| |w|h|e|r|e| |t|h|e| |w|o|r|d| |i|s| |a|l|s|o| >a|n|o|t|h|e|r| @29
+|~+0#4040ff13&| @73
+|~| @73
+|:+0#0000000&| @55|1@1|,|3|9| @8|A|l@1| 
diff --git a/src/testdir/test_popupwin.vim b/src/testdir/test_popupwin.vim
index c1bae36..29d02eb 100644
--- a/src/testdir/test_popupwin.vim
+++ b/src/testdir/test_popupwin.vim
@@ -2174,11 +2174,15 @@
         \ + ['this is another place']
         \ + range(29, 40),
         \ "Xtagfile")
+  call writefile(range(1,10)
+        \ + ['searched word is here']
+        \ + range(12, 20),
+        \ "Xheader.h")
   let lines =<< trim END
         set tags=Xtags
 	call setline(1, [
 	      \ 'one',
-	      \ 'two',
+	      \ '#include "Xheader.h"',
 	      \ 'three',
 	      \ 'four',
 	      \ 'five',
@@ -2189,6 +2193,9 @@
 	      \ 'this is another word',
 	      \ 'very long line where the word is also another'])
         set previewpopup=height:4,width:40
+	set path=.
+	call ch_logfile('logfile', 'w')
+	call ch_log('logfile started')
   END
   call writefile(lines, 'XtestPreviewPopup')
   let buf = RunVimInTerminal('-S XtestPreviewPopup', #{rows: 14})
@@ -2209,11 +2216,25 @@
 
   call term_sendkeys(buf, ":cd ..\<CR>:\<CR>")
   call VerifyScreenDump(buf, 'Test_popupwin_previewpopup_5', {})
+  call term_sendkeys(buf, ":cd testdir\<CR>")
+
+  call term_sendkeys(buf, ":pclose\<CR>")
+  call VerifyScreenDump(buf, 'Test_popupwin_previewpopup_6', {})
+
+  call term_sendkeys(buf, ":pedit +/theword Xtagfile\<CR>")
+  call term_sendkeys(buf, ":\<CR>")
+  call VerifyScreenDump(buf, 'Test_popupwin_previewpopup_7', {})
+
+  call term_sendkeys(buf, ":pclose\<CR>")
+  call term_sendkeys(buf, ":psearch searched\<CR>")
+  call term_sendkeys(buf, ":\<CR>")
+  call VerifyScreenDump(buf, 'Test_popupwin_previewpopup_8', {})
 
   call StopVimInTerminal(buf)
   call delete('Xtags')
   call delete('Xtagfile')
   call delete('XtestPreviewPopup')
+  call delete('Xheader.h')
 endfunc
 
 " vim: shiftwidth=2 sts=2