Origin: backport, commit:443ead70ac77c655095a67bfc0978145fda0c5de
Author: Matt McClinch <mattmcclinch@gmail.com>
Description: Fix #303619: MuseScore crashing when entering font name
 Resolves: https://musescore.org/en/node/303619.
 .
 Passing an empty string to QWidget::setStyleSheet() causes the widget's
 current style sheet to be removed, thus causing the widget's style to be
 inherited from its parent. This creates a problem in QComboBox::showPopup(),
 where it becomes possible that a pointer to a QStyle object could used after
 the object itself has been destroyed. A style sheet of " " can be used to
 override any previous style sheet without invalidating the current QStyle
 object.

--- a/mscore/inspector/inspectorBase.cpp
+++ b/mscore/inspector/inspectorBase.cpp
@@ -278,8 +278,8 @@ void InspectorBase::checkDifferentValues
                   }
             QColor c(preferences.globalStyle == MuseScoreStyleType::DARK ? Qt::yellow : Qt::blue);
 
-            // ii.w->setStyleSheet(valuesAreDifferent ? QString("* { color: %1 }").arg(MScore::selectColor[0].name()) : "");
-            ii.w->setStyleSheet(valuesAreDifferent ? QString("* { color: %1 }").arg(c.name()) : "");
+            // ii.w->setStyleSheet(valuesAreDifferent ? QString("* { color: %1 }").arg(MScore::selectColor[0].name()) : " ");
+            ii.w->setStyleSheet(valuesAreDifferent ? QString("* { color: %1 }").arg(c.name()) : " ");
             }
 
       //deal with reset if only one element, or if values are the same
@@ -293,12 +293,12 @@ void InspectorBase::checkDifferentValues
                   reset = false;
                   }
             else if (styledValue == PropertyStyle::UNSTYLED) {
-                  ii.w->setStyleSheet("");
+                  ii.w->setStyleSheet(" ");
                   reset = true;
                   }
             else {
                   reset = !isDefault(ii);
-                  ii.w->setStyleSheet("");
+                  ii.w->setStyleSheet(" ");
                   }
             if (ii.r)
                   ii.r->setEnabled(reset);
@@ -306,7 +306,7 @@ void InspectorBase::checkDifferentValues
       else {
             if (ii.r)
                   ii.r->setEnabled(true);
-            ii.w->setStyleSheet("");
+            ii.w->setStyleSheet(" ");
             }
       }