This closes qax-os#2102, fix panic on set chart title font (qax-os#2103)

- Update unit tests

Author: LZCZ

chart_test.go

@@ -219,7 +219,7 @@ func TestAddChart(t *testing.T) {
 		sheetName, cell string
 		opts            *Chart
 	}{
-		{sheetName: "Sheet1", cell: "P1", opts: &Chart{Type: Col, Series: series, Format: format, Legend: ChartLegend{Position: "none", ShowLegendKey: true}, Title: []RichTextRun{{Text: "2D Column Chart"}}, PlotArea: plotArea, Border: ChartLine{Type: ChartLineNone}, ShowBlanksAs: "zero", XAxis: ChartAxis{Font: Font{Bold: true, Italic: true, Underline: "dbl", Family: "Times New Roman", Size: 15, Strike: true, Color: "000000"}, Title: []RichTextRun{{Text: "Primary Horizontal Axis Title"}}}, YAxis: ChartAxis{Font: Font{Bold: false, Italic: false, Underline: "sng", Color: "777777"}, Title: []RichTextRun{{Text: "Primary Vertical Axis Title", Font: &Font{Color: "777777", Bold: true, Italic: true, Size: 12}}}}}},
+		{sheetName: "Sheet1", cell: "P1", opts: &Chart{Type: Col, Series: series, Format: format, Legend: ChartLegend{Position: "none", ShowLegendKey: true}, Title: []RichTextRun{{Text: "2D Column Chart", Font: &Font{Size: 11, Family: "Calibri"}}}, PlotArea: plotArea, Border: ChartLine{Type: ChartLineNone}, ShowBlanksAs: "zero", XAxis: ChartAxis{Font: Font{Bold: true, Italic: true, Underline: "dbl", Family: "Times New Roman", Size: 15, Strike: true, Color: "000000"}, Title: []RichTextRun{{Text: "Primary Horizontal Axis Title"}}}, YAxis: ChartAxis{Font: Font{Bold: false, Italic: false, Underline: "sng", Color: "777777"}, Title: []RichTextRun{{Text: "Primary Vertical Axis Title", Font: &Font{Color: "777777", Bold: true, Italic: true, Size: 12}}}}}},
 		{sheetName: "Sheet1", cell: "X1", opts: &Chart{Type: ColStacked, Series: series, Format: format, Legend: legend, Title: []RichTextRun{{Text: "2D Stacked Column Chart"}}, PlotArea: plotArea, Fill: Fill{Type: "pattern", Pattern: 1}, Border: ChartLine{Type: ChartLineAutomatic}, ShowBlanksAs: "zero", GapWidth: uintPtr(10), Overlap: intPtr(100)}},
 		{sheetName: "Sheet1", cell: "P16", opts: &Chart{Type: ColPercentStacked, Series: series, Format: format, Legend: legend, Title: []RichTextRun{{Text: "100% Stacked Column Chart"}}, PlotArea: plotArea, Fill: Fill{Type: "pattern", Color: []string{"EEEEEE"}, Pattern: 1}, Border: ChartLine{Type: ChartLineSolid, Width: 2}, ShowBlanksAs: "zero", XAxis: ChartAxis{Alignment: Alignment{Vertical: "wordArtVertRtl", TextRotation: 0}}}},
 		{sheetName: "Sheet1", cell: "X16", opts: &Chart{Type: Col3DClustered, Series: series, Format: format, Legend: ChartLegend{Position: "bottom", ShowLegendKey: false}, Title: []RichTextRun{{Text: "3D Clustered Column Chart"}}, PlotArea: plotArea, ShowBlanksAs: "zero"}},

drawing.go

@@ -1198,6 +1198,9 @@ func drawChartFont(fnt *Font, r *aRPr) {
 		r.SolidFill.SrgbClr = &attrValString{Val: stringPtr(strings.ReplaceAll(strings.ToUpper(fnt.Color), "#", ""))}
 	}
 	if fnt.Family != "" {
+		if r.Latin == nil {
+			r.Latin = &xlsxCTTextFont{}
+		}
 		r.Latin.Typeface = fnt.Family
 	}
 	if fnt.Size > 0 {