No NULL strings in SQL query for Gallery.

String fields filename, name, path (comment) and extension in database table gallery_files cannot be NULL.
Scanning the storage group for pictures can result in a database error like this:
2022-10-11 21:56:11.606192 E  Original query failed, but resend with empty strings in place of NULL strings worked.
DB Error (MSqlQuery):
Query was:
INSERT INTO gallery_files (file_id, filename, name, dir_id, type, modtime, size, extension, date, hidden, orientation, angle, path, zoom) VALUES (0, ?, ?,      ?, ?,   ?, ?,     ?, ?,   ?, ?, ?,    ?,   ?);
Bindings were:
:COMMENT="", :COVER=0, :DATE=1665518171, :EXTENSION=NULL, :FILEPATH="", :FS=0,
:HIDDEN=false, :MODTIME=1665518171, :NAME="", :ORIENT=0, :PARENT=0, :SIZE=0,
:TYPE=1
Driver error was [2/1048]:
QMYSQL3: Unable to execute statement
Database error was:
Column 'extension' cannot be null
This is fixed for all four string fields by using the bindValueNoNull function to bind the value.

mythtv/libs/libmythmetadata/imagemanager.cpp

@@ -817,17 +817,17 @@ int ImageDb<FS>::InsertDbImage(ImageItemK &im, bool checkForDuplicate) const
                           ":SIZE,     :EXTENSION, :DATE,   :HIDDEN, :ORIENT, "
                           ":COVER,    :COMMENT,   :FS);").arg(m_table, kDBColumns));
 
-    query.bindValue(":FILEPATH",  im.m_filePath);
-    query.bindValue(":NAME",      FS::BaseNameOf(im.m_filePath));
+    query.bindValueNoNull(":FILEPATH",  im.m_filePath);
+    query.bindValueNoNull(":NAME",      FS::BaseNameOf(im.m_filePath));
     query.bindValue(":FS",        im.m_device);
     query.bindValue(":PARENT",    FS::DbId(im.m_parentId));
     query.bindValue(":TYPE",      im.m_type);
     query.bindValue(":MODTIME",   static_cast<qint64>(im.m_modTime.count()));
     query.bindValue(":SIZE",      im.m_size);
-    query.bindValue(":EXTENSION", im.m_extension);
+    query.bindValueNoNull(":EXTENSION", im.m_extension);
     query.bindValue(":DATE",      static_cast<qint64>(im.m_date.count()));
     query.bindValue(":ORIENT",    im.m_orientation);
-    query.bindValueNoNull(":COMMENT", im.m_comment);
+    query.bindValueNoNull(":COMMENT",   im.m_comment);
     query.bindValue(":HIDDEN",    im.m_isHidden);
     query.bindValue(":COVER",     FS::DbId(im.m_userThumbnail));