Fix warning with type conversion from rune + int to string

Signed-off-by: Chris Cummer <chriscummer@me.com>

cfg/common_settings.go

@@ -124,12 +124,18 @@ func (common *Common) DefaultRowColor() string {
 	)
 }
 
+// FocusChar returns the keyboard number assigned to the widget used to give onscreen
+// focus to this widget, as a string. Focus characters can be a range between 1 and 9
 func (common *Common) FocusChar() string {
-	if common.focusChar <= -1 {
+	if common.focusChar <= 0 {
 		return ""
 	}
 
-	return string('0' + common.focusChar)
+	if common.focusChar > 9 {
+		return ""
+	}
+
+	return fmt.Sprint(common.focusChar)
 }
 
 func (common *Common) RowColor(idx int) string {

cfg/common_settings_test.go

@@ -47,29 +47,36 @@ func Test_DefaultRowColor(t *testing.T) {
 func Test_FocusChar(t *testing.T) {
 	tests := []struct {
 		name         string
-		expectedChar string
 		before       func(testCfg *Common)
+		expectedChar string
 	}{
 		{
-			name:         "with no focus char specified",
-			expectedChar: "",
+			name: "with negative focus char",
 			before: func(testCfg *Common) {
 				testCfg.focusChar = -1
 			},
+			expectedChar: "",
 		},
 		{
-			name:         "with explicit focus char specified",
-			expectedChar: "3",
+			name: "with positive focus char",
 			before: func(testCfg *Common) {
 				testCfg.focusChar = 3
 			},
+			expectedChar: "3",
 		},
 		{
-			name:         "with ridiculous focus char specified",
-			expectedChar: "Q",
+			name: "with zero focus char",
 			before: func(testCfg *Common) {
-				testCfg.focusChar = 33
+				testCfg.focusChar = 0
 			},
+			expectedChar: "",
+		},
+		{
+			name: "with large focus char",
+			before: func(testCfg *Common) {
+				testCfg.focusChar = 10
+			},
+			expectedChar: "",
 		},
 	}