Fix crash in indeterminate progressbars on windows

Note that this is a surgical fix for 4.7 only.
In 4.8 we will add these checks at the top
of the styling functions or in the widgets instead.

Task-number:QTBUG-15227
Reviewed-by:gabi
(cherry picked from commit 8a3c4c8283e4762744a29262ce507713565c1c0c)

2 files changed, 6 insertions, 3 deletions

diff --git a/src/gui/styles/qcommonstyle.cpp b/src/gui/styles/qcommonstyle.cpp
index c985c74aa5..8a9cda0b28 100644
--- a/src/gui/styles/qcommonstyle.cpp
+++ b/src/gui/styles/qcommonstyle.cpp
@@ -1402,8 +1402,9 @@ void QCommonStyle::drawControl(ControlElement element, const QStyleOption *opt,
         }
         break;
     case CE_ProgressBarGroove:
-        qDrawShadePanel(p, opt->rect, opt->palette, true, 1,
-                        &opt->palette.brush(QPalette::Window));
+        if (opt->rect.isValid())
+            qDrawShadePanel(p, opt->rect, opt->palette, true, 1,
+                            &opt->palette.brush(QPalette::Window));
         break;
     case CE_ProgressBarLabel:
         if (const QStyleOptionProgressBar *pb = qstyleoption_cast<const QStyleOptionProgressBar *>(opt)) {
diff --git a/src/gui/styles/qwindowsstyle.cpp b/src/gui/styles/qwindowsstyle.cpp
index 48a412ba1d..d2eb2192e6 100644
--- a/src/gui/styles/qwindowsstyle.cpp
+++ b/src/gui/styles/qwindowsstyle.cpp
@@ -2395,8 +2395,10 @@ void QWindowsStyle::drawControl(ControlElement ce, const QStyleOption *opt, QPai
 #ifndef QT_NO_PROGRESSBAR
     case CE_ProgressBarContents:
         if (const QStyleOptionProgressBar *pb = qstyleoption_cast<const QStyleOptionProgressBar *>(opt)) {
-
             QRect rect = pb->rect;
+            if (!rect.isValid())
+                return;
+
             bool vertical = false;
             bool inverted = false;