Fix -Wimplicit-fallthrough for clang

Clang's `-Wimplicit-fallthrough` warnings are a little stricter than
gcc's interpretation:

switch (i) {
case 0:
    foo();
case 4:
    break;
}

While gcc accepts the implicit fallthrough, if the following statement
is a trivial `break`, clang will warn about it.

Pick-to: 6.7
Change-Id: I38e0817f1bc034fbb552aeac21de1516edcbcbb0
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

1 files changed, 1 insertions, 0 deletions

diff --git a/src/widgets/widgets/qabstractspinbox.cpp b/src/widgets/widgets/qabstractspinbox.cpp
index 27bc9e9099..f377275d23 100644
--- a/src/widgets/widgets/qabstractspinbox.cpp
+++ b/src/widgets/widgets/qabstractspinbox.cpp
@@ -2043,6 +2043,7 @@ QVariant operator-(const QVariant &arg1, const QVariant &arg2)
                 dt.setTime(dt.time().addMSecs(msecs));
             ret = QVariant(dt);
         }
+        break;
     }
     default: break;
     }