Replace NULL by '\0' in some char comparison

fix some Warning: pointer-arith in Player.cpp

Signed-off-by: XoD <xoddark@gmail.com>

neo/d3xp/Player.cpp

@@ -4140,7 +4140,7 @@ idPlayer::GiveVideo
 */
 void idPlayer::GiveVideo( const char *videoName, idDict *item ) {
 
-	if ( videoName == NULL || *videoName == NULL ) {
+	if ( videoName == NULL || *videoName == '\0' ) {
 		return;
 	}
 
@@ -4177,7 +4177,7 @@ idPlayer::GiveEmail
 */
 void idPlayer::GiveEmail( const char *emailName ) {
 
-	if ( emailName == NULL || *emailName == NULL ) {
+	if ( emailName == NULL || *emailName == '\0' ) {
 		return;
 	}
 
@@ -4204,7 +4204,7 @@ void idPlayer::GivePDA( const char *pdaName, idDict *item )
 		inventory.pdaSecurity.AddUnique( item->GetString( "inv_name" ) );
 	}
 
-	if ( pdaName == NULL || *pdaName == NULL ) {
+	if ( pdaName == NULL || *pdaName == '\0' ) {
 		pdaName = "personal";
 	}
 
@@ -6297,7 +6297,7 @@ void idPlayer::UpdatePDAInfo( bool updatePDASel ) {
 
 		const char *security = pda->GetSecurity();
 		if ( j == currentPDA || (currentPDA == 0 && security && *security ) ) {
-			if ( *security == NULL ) {
+			if ( *security == '\0' ) {
 				security = common->GetLanguageDict()->GetString( "#str_00066" );
 			}
 			objectiveSystem->SetStateString( "PDASecurityClearance", security );