Eagle: Fix crash when importing Eagle V6

This fixes multiple issues when importing Eagle V6 files.

Crashes occured when arcs of 0-length were found and when parts were
referenced in the schematic that were not found in the library.  This
could happen if the library and schematic were different cases.

Fixes: lp:1830564
* https://bugs.launchpad.net/kicad/+bug/1830564

common/eagle_parser.cpp

@@ -109,7 +109,9 @@ long long int ECOORD::ConvertToNm( int aValue, enum EAGLE_UNIT aUnit )
         case EU_MIL:   ret = (long long) aValue * 25400; break;
     }
 
-    wxASSERT( ( ret > 0 ) == ( aValue > 0 ) );  // check for overflow
+    if( ( ret > 0 ) != ( aValue > 0 ) )
+        wxLogError( _( "Invalid size %lld: too large" ), aValue );
+
     return ret;
 }
 
@@ -283,8 +285,13 @@ wxPoint ConvertArcCenter( const wxPoint& aStart, const wxPoint& aEnd, double aAn
     wxPoint mid = ( aStart + aEnd ) / 2;
 
     double dlen = sqrt( dx*dx + dy*dy );
-    wxASSERT( dlen != 0 );
-    wxASSERT( aAngle != 0 );
+
+    if( !std::isnormal( dlen ) || !std::isnormal( aAngle ) )
+    {
+        THROW_IO_ERROR(
+                wxString::Format( _( "Invalid Arc with radius %f and angle %f" ), dlen, aAngle ) );
+    }
+
     double dist = dlen / ( 2 * tan( DEG2RAD( aAngle ) / 2 ) );
 
     wxPoint center(
@@ -608,7 +615,7 @@ wxSize ETEXT::ConvertSize() const
         }
         else
         {
-            wxASSERT( false );
+            wxLogDebug( "Invalid font name \"%s\"", fontName );
             textsize = wxSize( size.ToSchUnits(), size.ToSchUnits() );
         }
     }

eeschema/class_libentry.cpp

@@ -550,7 +550,8 @@ void LIB_PART::RemoveDrawItem( LIB_ITEM* aItem, EDA_DRAW_PANEL* aPanel, wxDC* aD
 
 void LIB_PART::AddDrawItem( LIB_ITEM* aItem )
 {
-    wxASSERT( aItem != NULL );
+    if( !aItem )
+        return;
 
     m_drawings.push_back( aItem );
 }

eeschema/sch_eagle_plugin.cpp

@@ -533,7 +533,9 @@ void SCH_EAGLE_PLUGIN::loadSchematic( wxXmlNode* aSchematicNode )
     while( partNode )
     {
         std::unique_ptr<EPART> epart( new EPART( partNode ) );
-        m_partlist[epart->name] = std::move( epart );
+
+        // N.B. Eagle parts are case-insensitive in matching but we keep the display case
+        m_partlist[epart->name.Upper()] = std::move( epart );
         partNode = partNode->GetNext();
     }
 
@@ -1061,7 +1063,18 @@ void SCH_EAGLE_PLUGIN::loadInstance( wxXmlNode* aInstanceNode )
     // Calculate the unit number from the gate entry of the instance
     // Assign the the LIB_ID from deviceset and device names
 
-    EPART* epart = m_partlist[einstance.part].get();
+    auto part_it = m_partlist.find( einstance.part.Upper() );
+
+    if( part_it == m_partlist.end() )
+    {
+        wxLogError( _( "Error parsing Eagle file.  "
+                       "Could not find \"%s\" instance but it is referenced in the schematic." ),
+                einstance.part );
+
+        return;
+    }
+
+    EPART* epart = part_it->second.get();
 
     wxString libraryname = epart->library;
     wxString gatename = epart->deviceset + epart->device + einstance.gate;
@@ -1565,6 +1578,9 @@ LIB_ITEM* SCH_EAGLE_PLUGIN::loadSymbolWire( std::unique_ptr<LIB_PART>& aPart,
     end.x   = ewire.x2.ToSchUnits();
     end.y   = ewire.y2.ToSchUnits();
 
+    if( begin == end )
+        return nullptr;
+
     // if the wire is an arc
     if( ewire.curve )
     {