when wrong channel is selected (via url) show error (#178)

src/Main.elm

@@ -117,7 +117,11 @@ submitQuery :
 submitQuery old ( new, cmd ) =
     let
         triggerSearch _ newModel msg makeRequest =
-            if newModel.query /= Nothing && newModel.query /= Just "" then
+            if
+                (newModel.query /= Nothing)
+                    && (newModel.query /= Just "")
+                    && List.member newModel.channel Search.channels
+            then
                 ( new
                 , Cmd.batch
                     [ cmd

src/Search.elm

@@ -6,6 +6,7 @@ module Search exposing
     , SearchResult
     , Sort(..)
     , channelDetailsFromId
+    , channels
     , decodeResult
     , fromSortId
     , init
@@ -463,6 +464,20 @@ view path title model viewSuccess outMsg =
             [ form [ onSubmit (outMsg QueryInputSubmit) ]
                 [ p
                     []
+                    ([]
+                        |> List.append
+                            (if List.member model.channel channels then
+                                []
+
+                             else
+                                [ p [ class "alert alert-error" ]
+                                    [ h4 [] [ text "Wrong channel selected!" ]
+                                    , text <| "Please select one of the channels above!"
+                                    ]
+                                ]
+                            )
+                        |> List.append
+                            [ p []
                                 [ strong []
                                     [ text "Channel: " ]
                                 , div
@@ -488,6 +503,8 @@ view path title model viewSuccess outMsg =
                                         channels
                                     )
                                 ]
+                            ]
+                    )
                 , p
                     [ class "input-append"
                     ]