fix: set min-height qss for vertical handle(when to show thousands data, handle too small)

Author: muyr

dayu_widgets/static/main.qss

@@ -1054,6 +1054,7 @@ QScrollBar:vertical {
 
 QScrollBar::handle:vertical {
     background-color: @background_selected_color;
+    min-height: @scroll_bar_min_length@unit;
 }
 
 QScrollBar::add-line:vertical {

dayu_widgets/theme.py

@@ -95,6 +95,7 @@ def get_theme_size():
         "indicator_padding": int(4 * scale_factor_x),
         "indicator_size": int(8 * scale_factor_x),
         "scroll_bar_size": int(12 * scale_factor_x),
+        "scroll_bar_min_length": int(20 * scale_factor_x),
         "scroll_bar_margin": int(12 * scale_factor_x * 2) + 1,
         "scroll_bar_radius": int(12 * scale_factor_x / 2.0),
     }