More gracefully handle tinyspline not liking a spline definition

Partial fix for #6634

(cherry picked from commit e409b04538)

pcbnew/import_gfx/dxf_import_plugin.cpp

@@ -161,7 +161,7 @@ bool DXF_IMPORT_PLUGIN::ImportDxfFile( const wxString& aFile )
 }
 
 
-void DXF_IMPORT_PLUGIN::reportMsg( const char* aMessage )
+void DXF_IMPORT_PLUGIN::reportMsg( const wxString& aMessage )
 {
     // Add message to keep trace of not handled dxf entities
     m_messages += aMessage;
@@ -1050,8 +1050,6 @@ void DXF_IMPORT_PLUGIN::insertSpline( int aWidth )
         }
     }
 #else   // Use bezier curves, supported by pcbnew, to approximate the spline
-	tinyspline::BSpline dxfspline( m_curr_entity.m_SplineControlPointList.size(),
-                                   /* coord dim */ 2, m_curr_entity.m_SplineDegree );
     std::vector<double> ctrlp;
 
     for( unsigned ii = 0; ii < imax; ++ii )
@@ -1060,11 +1058,31 @@ void DXF_IMPORT_PLUGIN::insertSpline( int aWidth )
         ctrlp.push_back( m_curr_entity.m_SplineControlPointList[ii].m_y );
     }
 
+    std::vector<double> coords;
+    try
+    {
+	    tinyspline::BSpline dxfspline( m_curr_entity.m_SplineControlPointList.size(),
+                                       /* coord dim */ 2, m_curr_entity.m_SplineDegree );
+
 	    dxfspline.setCtrlp( ctrlp );
 	    dxfspline.setKnots( m_curr_entity.m_SplineKnotsList );
 	    tinyspline::BSpline beziers( dxfspline.toBeziers() );
 
-    std::vector<double> coords = beziers.ctrlp();
+        coords = beziers.ctrlp();
+    }
+    catch( const std::runtime_error& )  //tinyspline throws everything including data validation as runtime errors
+    {
+        // invalid spline definition, drop this block
+        reportMsg( _( "Invalid spline definition encountered" ) );
+        return;
+    }
+
+    if( coords.size() % 8 != 0 )
+    {
+        // somehow we generated a bad Bezier curve
+        reportMsg( _( "Invalid Bezier curve created" ) );
+        return;
+    }
 
     // Each Bezier curve uses 4 vertices (a start point, 2 control points and a end point).
     // So we can have more than one Bezier curve ( there are one curve each four vertices)

pcbnew/import_gfx/dxf_import_plugin.h

@@ -217,14 +217,14 @@ public:
     /**
      * @return the list of messages in one string. Each message ends by '\n'
      */
-    const std::string& GetMessages() const override
+    const wxString& GetMessages() const override
     {
         return m_messages;
     }
 
 private:
     // report message to keep trace of not supported dxf entities:
-    void reportMsg( const char* aMessage );
+    void reportMsg( const wxString& aMessage );
 
     // coordinate conversions from dxf file to mm
     double mapX( double aDxfCoordX );

pcbnew/import_gfx/graphics_import_plugin.h

@@ -118,7 +118,7 @@ public:
      *
      * @return the list of messages in one string. Each message ends by '\n'
      */
-    const virtual std::string& GetMessages() const = 0;
+    const virtual wxString& GetMessages() const = 0;
 
 protected:
     ///> Importer used to create objects representing the imported shapes.

pcbnew/import_gfx/graphics_importer.h

@@ -83,7 +83,7 @@ public:
      *
      * @return the list of messages in one string. Each message ends by '\n'
      */
-    const std::string& GetMessages() const
+    const wxString& GetMessages() const
     {
         return m_plugin->GetMessages();
     }

pcbnew/import_gfx/svg_import_plugin.h

@@ -52,7 +52,7 @@ public:
     /**
      * @return the list of messages in one string. Each message ends by '\n'
      */
-    const std::string& GetMessages() const override
+    const wxString& GetMessages() const override
     {
         return m_messages;
     }
@@ -77,7 +77,7 @@ private:
 
     struct NSVGimage* m_parsedImage;
 
-    std::string m_messages;     // messages generated during svg file parsing.
+    wxString m_messages; // messages generated during svg file parsing.
                                 // Each message ends by '\n'
 };