fix "remove value" not working in conditional property panel
fix "remove value" not working in conditional property panel

refs #132

citation-style-editor/csl-editor,citation-style-editor/csl-editor,adam3smith/csl-editor,citation-style-language/csl-editor,citation-style-editor/csl-editor,adam3smith/csl-editor,citation-style-language/csl-editor,fbennett/csl-editor,adam3smith/csl-editor,fbennett/csl-editor,citation-style-language/csl-editor