Windows: fix URI association setting in registry

- fix for #1877
- fix was reported to work via
  https://bitcointalk.org/index.php?topic=110243.msg1230418#msg1230418

share/setup.nsi

@@ -101,7 +101,7 @@ Section -post SEC0001
     WriteRegStr HKCR "bitcoin" "URL Protocol" ""
     WriteRegStr HKCR "bitcoin" "" "URL:Bitcoin"
     WriteRegStr HKCR "bitcoin\DefaultIcon" "" $INSTDIR\bitcoin-qt.exe
-    WriteRegStr HKCR "bitcoin\shell\open\command" "" '"$INSTDIR\bitcoin-qt.exe" "$$1"'
+    WriteRegStr HKCR "bitcoin\shell\open\command" "" '"$INSTDIR\bitcoin-qt.exe" "%1"'
 SectionEnd
 
 # Macro for selecting uninstaller sections