platforms/drm: don't ignore blob properties without valid blobs

Instead of deleting all blob properties without a valid
blob check for the blob existing before using it. This is
necessary because some properties are needed even without
currently valid blobs.

BUG: 435786

src/plugins/platforms/drm/drm_object.cpp

@@ -52,9 +52,6 @@ bool DrmObject::initProps(const QVector<PropertyDefinition> &&vector, uint32_t o
                 drmModePropertyBlobRes *blob = nullptr;
                 if (prop->flags & DRM_MODE_PROP_BLOB) {
                     blob = drmModeGetPropertyBlob(m_gpu->fd(), properties->prop_values[i]);
-                    if (!blob) {
-                        break;
-                    }
                 }
                 qCDebug(KWIN_DRM, "Found property %s with value %lu", def.name.data(), properties->prop_values[i]);
                 m_props[j] = new Property(prop.data(), properties->prop_values[i], def.enumNames, blob);

src/plugins/platforms/drm/drm_object_connector.cpp

@@ -50,15 +50,16 @@ bool DrmConnector::init()
     }
 
     // parse edid
-    if (auto edidProp = m_props[static_cast<uint32_t>(PropertyIndex::Edid)]) {
+    auto edidProp = m_props[static_cast<uint32_t>(PropertyIndex::Edid)];
+    if (edidProp && edidProp->blob() && edidProp->blob()->data) {
         m_edid = Edid(edidProp->blob()->data, edidProp->blob()->length);
         if (!m_edid.isValid()) {
             qCWarning(KWIN_DRM, "Couldn't parse EDID for connector with id %d", id());
         }
-        deleteProp(PropertyIndex::Edid);
     } else {
         qCDebug(KWIN_DRM) << "Could not find edid for connector" << this;
     }
+    deleteProp(PropertyIndex::Edid);
 
     // check the physical size
     if (m_edid.physicalSize().isEmpty()) {