Discard mouse button up events if no button is currently pressed.

dlls/comctl32/toolbar.c

diff --git a/dlls/comctl32/toolbar.c b/dlls/comctl32/toolbar.c
index 3811828..8c1c67e 100644
--- a/dlls/comctl32/toolbar.c
+++ b/dlls/comctl32/toolbar.c
@@ -5042,6 +5042,7 @@
     if((infoPtr->nHotItem >= 0) && (nHit != -1))
         infoPtr->buttons[infoPtr->nHotItem].bHot = TRUE;
 
+    if (0 <= infoPtr->nButtonDown) {
 	btnPtr = &infoPtr->buttons[infoPtr->nButtonDown];
 	btnPtr->fsState &= ~TBSTATE_PRESSED;
 
@@ -5111,6 +5112,7 @@
 	    nmmouse.dwItemData = btnPtr->dwData;
 	    TOOLBAR_SendNotify ((NMHDR *) &nmmouse, infoPtr, NM_CLICK);
 	}
+    }
     return 0;
 }