Fix search filter update

Author: GuillaumeGomez

src/librustdoc/html/static/search.js

@@ -1442,6 +1442,10 @@ window.initSearch = function(rawSearchIndex) {
         if (selectCrate) {
             selectCrate.onchange = function() {
                 updateLocalStorage("rustdoc-saved-filter-crate", selectCrate.value);
+                // In case you "cut" the entry from the search input, then change the crate filter
+                // before paste back the previous search, you get the old search results without
+                // the filter. To prevent this, we need to remove the previous results.
+                currentResults = null;
                 search(undefined, true);
             };
         }

src/test/rustdoc-gui/search-filter.goml

@@ -0,0 +1,17 @@
+goto: file://|DOC_PATH|/test_docs/index.html
+write: (".search-input", "test")
+// Waiting for the search results to appear...
+wait-for: "#titles"
+assert-text: ("#results .externcrate", "test_docs")
+text: (".search-input", "")
+// We now want to change the crate filter.
+click: "#crate-search"
+// We select "lib2" option then press enter to change the filter.
+press-key: "ArrowDown"
+press-key: "Enter"
+// We now make the search again.
+write: (".search-input", "test")
+// Waiting for the search results to appear...
+wait-for: "#titles"
+// We check that there is no more "test_docs" appearing.
+assert-false: "#results .externcrate"