Do not assert when preferred{Width|Height} is infinity

This adds an autotest for the fix that landed in qtbase:
(2a95ecf7e81fbdcfad50f8a1dd5c62b120e2ec27)

Task-number: QTBUG-116577
Pick-to: 6.7 6.6 6.5
Change-Id: I143f969596c6ee7ccd3d8607cfa53d539566a0b5
Reviewed-by: Santhosh Kumar <santhosh.kumar.selvaraj@qt.io>

tests/auto/quick/qquicklayouts/data/tst_rowlayout.qml

@@ -945,7 +945,19 @@ Item {
                     },
                     layoutWidth:     0,
                     expectedWidths: [0]
-                  }
+                },{
+                  tag: "preferred_infinity",    // Do not crash/assert when the preferred size is infinity
+                  layout: {
+                    type: "RowLayout",
+                    items: [
+                        {minimumWidth:  10, preferredWidth: Number.POSITIVE_INFINITY, fillWidth: true},
+                        {minimumWidth:  20, preferredWidth: Number.POSITIVE_INFINITY, fillWidth: true},
+                      ]
+                  },
+                  layoutWidth:     31,      // Important that this is between minimum and preferred width of the layout.
+                  expectedWidths: [10, 21]  // The result here does not have to be exact. (This
+                                            // test is mostly concerned about not crashing).
+                }
             ];
         }