When no keywords to search, use an empty query selection that evaluates to "1".

This means that instead of building invalid SQL such as `WHERE (() OR ())` it
will build `WHERE((1) OR (1))` which, while non-optimal, is at least valid.

Fixes issue #560.

CHANGELOG.md

@@ -1,3 +1,7 @@
+### Upcoming Release
+
+* Fix bug when entering only a space into the search dialog.
+
 ### 0.98 (2015-02-02)
 
 * Add opt-in crash reporting via ACRA

F-Droid/src/org/fdroid/fdroid/data/AppProvider.java

@@ -614,15 +614,14 @@ public class AppProvider extends FDroidProvider {
     }
 
     private AppQuerySelection querySearch(String query) {
-        final String[] columns = {
+        // Put in a Set to remove duplicates
-                getTableName() + ".id",
-                getTableName() + ".name",
-                getTableName() + ".summary",
-                getTableName() + ".description",
-        };
-
-        // Remove duplicates, surround in % for wildcard searching
         final Set<String> keywordSet = new HashSet<>(Arrays.asList(query.split("\\s")));
+
+        if (keywordSet.size() == 0) {
+            return new AppQuerySelection();
+        }
+
+        // Surround each keyword in % for wildcard searching
         final String[] keywords = new String[keywordSet.size()];
         int iKeyword = 0;
         for (final String keyword : keywordSet) {
@@ -630,6 +629,13 @@ public class AppProvider extends FDroidProvider {
             iKeyword++;
         }
 
+        final String[] columns = {
+            getTableName() + ".id",
+            getTableName() + ".name",
+            getTableName() + ".summary",
+            getTableName() + ".description",
+        };
+
         // Build selection string and fill out keyword arguments
         final StringBuilder selection = new StringBuilder();
         final String[] selectionKeywords = new String[columns.length * keywords.length];