Fix expand variables for built-in

Allow falling back to the alternate variable definitions if the built-in
text block variables are not set.

Also push the project into variable resolution when plotting

Fixes https://gitlab.com/kicad/code/kicad/issues/11168

(cherry picked from commit c44d31fcfb)

common/title_block.cpp

@@ -94,8 +94,13 @@ bool TITLE_BLOCK::TextVarResolver( wxString* aToken, const PROJECT* aProject ) c
 
     if( aToken->IsSameAs( wxT( "ISSUE_DATE" ) ) )
     {
-        *aToken = GetDate();
-        tokenUpdated = true;
+        wxString ret = GetDate();
+
+        if( !ret.empty() )
+        {
+            *aToken = ret;
+            tokenUpdated = true;
+        }
     }
     else if( aToken->IsSameAs( wxT( "CURRENT_DATE" ) ) )
     {
@@ -111,18 +116,33 @@ bool TITLE_BLOCK::TextVarResolver( wxString* aToken, const PROJECT* aProject ) c
     }
     else if( aToken->IsSameAs( wxT( "REVISION" ) ) )
     {
-        *aToken = GetRevision();
-        tokenUpdated = true;
+        wxString ret = GetRevision();
+
+        if( !ret.empty() )
+        {
+            *aToken = ret;
+            tokenUpdated = true;
+        }
     }
     else if( aToken->IsSameAs( wxT( "TITLE" ) ) )
     {
-        *aToken = GetTitle();
-        tokenUpdated = true;
+        wxString ret = GetTitle();
+
+        if( !ret.empty() )
+        {
+            *aToken = ret;
+            tokenUpdated = true;
+        }
     }
     else if( aToken->IsSameAs( wxT( "COMPANY" ) ) )
     {
-        *aToken = GetCompany();
-        tokenUpdated = true;
+        wxString ret = GetCompany();
+
+        if( !ret.empty() )
+        {
+            *aToken = ret;
+            tokenUpdated = true;
+        }
     }
     else if( aToken->Left( aToken->Len() - 1 ).IsSameAs( wxT( "COMMENT" ) ) )
     {
@@ -139,8 +159,13 @@ bool TITLE_BLOCK::TextVarResolver( wxString* aToken, const PROJECT* aProject ) c
         case '7':
         case '8':
         case '9':
-            *aToken = GetComment( c - '1' );
-            tokenUpdated = true;
+            wxString ret = GetComment( c - '1' );
+
+            if( !ret.empty() )
+            {
+                *aToken = ret;
+                tokenUpdated = true;
+            }
         }
     }
 

pcbnew/dialogs/dialog_plot.cpp

@@ -806,7 +806,7 @@ void DIALOG_PLOT::Plot( wxCommandEvent& event )
             };
 
     wxString path = m_plotOpts.GetOutputDirectory();
-    path = ExpandTextVars( path, &textResolver, nullptr, nullptr );
+    path = ExpandTextVars( path, &textResolver, nullptr, board->GetProject() );
     path = ExpandEnvVarSubstitutions( path, nullptr );
 
     wxFileName outputDir = wxFileName::DirName( path );