One more pylint fix

Signed-off-by: falkTX <falktx@falktx.com>

.travis/script-pylint.sh

@@ -19,7 +19,9 @@ ${pylint} \
     --max-line-length=120 \
     --max-locals=25 \
     --max-statements=100 \
-    --enable=bad-continuation \
+    --enable=\
+bad-continuation,\
+len-as-condition \
     --disable=\
 bad-whitespace,\
 broad-except,\

source/frontend/widgets/racklistwidget.py

@@ -316,7 +316,7 @@ class RackListWidget(QListWidget):
 
         urls = event.mimeData().urls()
 
-        if len(urls) == 0:
+        if not urls:
             return
 
         tryItem = self.itemAt(event.pos())