Fixes a minibuffer/cmdline completion bug

If the user opened the cmdline and typed "help ", four completions would
be correctly offered for help subarguments. But if the user then hit
tab, the cmdline expanded incorrectly to "help help".

ui/ui.go

@@ -1353,11 +1353,6 @@ func lastLineMode(app gowid.IApp) {
 		return nil
 	}))
 
-	MiniBuffer.Register("help", minibufferFn(func(gowid.IApp, ...string) error {
-		OpenTemplatedDialog(appView, "UIHelp", app)
-		return nil
-	}))
-
 	MiniBuffer.Register("no-theme", minibufferFn(func(app gowid.IApp, s ...string) error {
 		mode := theme.Mode(app.GetColorMode()).String() // more concise
 		termshark.DeleteConf(fmt.Sprintf("main.theme-%s", mode))

widgets/minibuffer/minibuffer.go

@@ -294,10 +294,14 @@ func (w *Widget) handleSelection(keyIsEnter bool, app gowid.IApp) {
 						extraPrefix += string(c)
 					}
 					longestPrefixPartial := partials[selectedIdx]
-					// e.g. "cl" + "ear-" from ["clear-packets", "clear-filter"]
-					longestPrefixPartial.qword = words[len(words)-1] + extraPrefix
-					w.ed.SetText(longestPrefixPartial.Line(), app)
-					w.ed.SetCursorPos(longestPrefixPartial.CursorPos(), app)
+					// if the user types e.g. "help " then hits tab, extraPrefix will be "" (no characters typed
+					// to start selection of next argument) so don't complete.
+					if extraPrefix != "" {
+						// e.g. "cl" + "ear-" from ["clear-packets", "clear-filter"]
+						longestPrefixPartial.qword = words[len(words)-1] + extraPrefix
+						w.ed.SetText(longestPrefixPartial.Line(), app)
+						w.ed.SetCursorPos(longestPrefixPartial.CursorPos(), app)
+					}
 				}
 			}
 		}