Report id: 1393122152
I'm using WebDAV by NextCloud, and I'm sure that NextCloud works normally.
But when I try to make a Syncing, it will be unsuccessful.


```
[JavaScript Error: "obj.toJSON is not a function" {file: "chrome://zotero/content/xpcom/sync/syncEngine.js" line: 1543}]

[JavaScript Error: "Key not provided"]

[JavaScript Error: "Key not provided"]

[JavaScript Error: "Key not provided"]

[JavaScript Error: "obj.toJSON is not a function" {file: "chrome://zotero/content/xpcom/sync/syncEngine.js" line: 1543}]

[JavaScript Error: "obj.toJSON is not a function" {file: "chrome://zotero/content/xpcom/sync/syncEngine.js" line: 1543}]

[JavaScript Error: "Key not provided"]

[JavaScript Error: "Key not provided"]

[JavaScript Error: "Key not provided"]

[JavaScript Error: "obj.toJSON is not a function" {file: "chrome://zotero/content/xpcom/sync/syncEngine.js" line: 1543}]

[JavaScript Error: "obj.toJSON is not a function" {file: "chrome://zotero/content/xpcom/sync/syncEngine.js" line: 1543}]

[JavaScript Error: "Key not provided"]

[JavaScript Error: "Key not provided"]

[JavaScript Error: "Key not provided"]

[JavaScript Error: "obj.toJSON is not a function" {file: "chrome://zotero/content/xpcom/sync/syncEngine.js" line: 1543}]

[JavaScript Error: "obj.toJSON is not a function" {file: "chrome://zotero/content/xpcom/sync/syncEngine.js" line: 1543}]

[JavaScript Error: "Key not provided"]

[JavaScript Error: "Key not provided"]

[JavaScript Error: "Key not provided"]

[JavaScript Error: "obj.toJSON is not a function" {file: "chrome://zotero/content/xpcom/sync/syncEngine.js" line: 1543}]

[JavaScript Error: "obj.toJSON is not a function" {file: "chrome://zotero/content/xpcom/sync/syncEngine.js" line: 1543}]

[JavaScript Error: "NS_ERROR_NOT_AVAILABLE: Cannot call openModalWindow on a hidden window" {file: "jar:file:///C:/Program%20Files%20(x86)/Zotero/omni.ja!/components/nsPrompter.js" line: 340}]

[JavaScript Error: "[Exception... "Cannot call openModalWindow on a hidden window" nsresult: "0x80040111 (NS_ERROR_NOT_AVAILABLE)" location: "JS frame :: jar:file:///C:/Program%20Files%20(x86)/Zotero/omni.ja!/components/nsPrompter.js :: openModalWindow :: line 340" data: no]"]
openModalWindow@jar:file:///C:/Program%20Files%20(x86)/Zotero/omni.ja!/components/nsPrompter.js:340:19
openPrompt@jar:file:///C:/Program%20Files%20(x86)/Zotero/omni.ja!/components/nsPrompter.js:563:9
confirm@jar:file:///C:/Program%20Files%20(x86)/Zotero/omni.ja!/components/nsPrompter.js:644:9
CheckTransShortcutsStyle@chrome://zoteroif/content/scripts/preferences.js:89:23
initPreferences@chrome://zoteroif/content/scripts/preferences.js:16:5
anonymous@chrome://zotero/content/bindings/preferences-win.xml line 768 > Function:3:1
_fireEvent@chrome://zotero/content/bindings/preferences-win.xml:769:24
prefwindow_XBL_Constructor@chrome://zotero/content/bindings/preferences-win.xml:646:13


[JavaScript Error: "NS_ERROR_NOT_AVAILABLE: Cannot call openModalWindow on a hidden window" {file: "jar:file:///C:/Program%20Files%20(x86)/Zotero/omni.ja!/components/nsPrompter.js" line: 340}]

[JavaScript Error: "[Exception... "Cannot call openModalWindow on a hidden window" nsresult: "0x80040111 (NS_ERROR_NOT_AVAILABLE)" location: "JS frame :: jar:file:///C:/Program%20Files%20(x86)/Zotero/omni.ja!/components/nsPrompter.js :: openModalWindow :: line 340" data: no]"]
openModalWindow@jar:file:///C:/Program%20Files%20(x86)/Zotero/omni.ja!/components/nsPrompter.js:340:19
openPrompt@jar:file:///C:/Program%20Files%20(x86)/Zotero/omni.ja!/components/nsPrompter.js:563:9
confirm@jar:file:///C:/Program%20Files%20(x86)/Zotero/omni.ja!/components/nsPrompter.js:644:9
CheckTransShortcutsStyle@chrome://zoteroif/content/scripts/preferences.js:89:23
initPreferences@chrome://zoteroif/content/scripts/preferences.js:16:5
anonymous@chrome://zotero/content/bindings/preferences-win.xml line 768 > Function:3:1
_fireEvent@chrome://zotero/content/bindings/preferences-win.xml:769:24
prefwindow_XBL_Constructor@chrome://zotero/content/bindings/preferences-win.xml:646:13
```