fix contrast not increment to limit value between 0.0 & 1.0

Change-Id: I1a8c08fb8f704e69ae1ae75d77784f07a1d99a12

vbahelper/source/vbahelper/vbapictureformat.cxx

@@ -103,15 +103,15 @@ void SAL_CALL
 ScVbaPictureFormat::IncrementContrast( double increment ) throw (uno::RuntimeException)
 {
     double nContrast = getContrast();
-    if( increment < 0 )
+    nContrast += increment;
+    if( nContrast < 0 )
     {
-        increment = 0.0;
+        nContrast = 0.0;
     }
-    if( increment > 1 )
+    if( nContrast > 1 )
     {
-        increment = 1.0;
+        nContrast = 1.0;
     }
-    nContrast += increment;
     setContrast( nContrast );
 }