Fix #11972: Incorrect minimum width allocated to graph. (#11974)

Width was based on actual number of data points instead of possible number of data points.

src/graph_gui.cpp

@@ -548,7 +548,7 @@ public:
 		SetDParam(1, INT64_MAX);
 		uint y_label_width = GetStringBoundingBox(STR_GRAPH_Y_LABEL).width;
 
-		size->width  = std::max<uint>(size->width,  ScaleGUITrad(5) + y_label_width + this->num_on_x_axis * (x_label_width + ScaleGUITrad(5)) + ScaleGUITrad(9));
+		size->width  = std::max<uint>(size->width,  ScaleGUITrad(5) + y_label_width + this->num_vert_lines * (x_label_width + ScaleGUITrad(5)) + ScaleGUITrad(9));
 		size->height = std::max<uint>(size->height, ScaleGUITrad(5) + (1 + MIN_GRAPH_NUM_LINES_Y * 2 + (this->draw_dates ? 3 : 1)) * GetCharacterHeight(FS_SMALL) + ScaleGUITrad(4));
 		size->height = std::max<uint>(size->height, size->width / 3);
 	}