Do not allow negative qty_multiplier

Co-authored-by: kvid <kvid@users.noreply.github.com>

src/wireviz/DataClasses.py

@@ -233,7 +233,7 @@ def get_qty_multiplier(self, qty_multiplier: Optional[ConnectorMultiplier]) -> i
         elif qty_multiplier == "populated":
             return sum(self.visible_pins.values())
         elif qty_multiplier == 'unpopulated':
-            return (self.pincount - sum(self.visible_pins.values()))
+            return max(0, self.pincount - sum(self.visible_pins.values()))
         else:
             raise ValueError(
                 f"invalid qty multiplier parameter for connector {qty_multiplier}"