+ split file extension from descriptive text of file format to avoid that invalid translation breaks file dialog

+ add method to make image view unclosable for user
+ fix possible crash in MeshAlgorithm::GetMeshBorder
+ fix possible crash in MeshAlgorithm::ConnectLines

src/Mod/Mesh/App/Core/Degeneration.cpp

@@ -659,7 +659,7 @@ bool MeshFixDeformedFacets::Fixup()
         fCosAngles[i] = fCosAngle;
       }
 
-      // first check for angle > 120°: in this case we swap with the opposite edge
+      // first check for angle > 120 deg: in this case we swap with the opposite edge
       for (int i=0; i<3; i++)
       {
         float fCosAngle = fCosAngles[i];
@@ -678,7 +678,7 @@ bool MeshFixDeformedFacets::Fixup()
       if (done)
         continue;
 
-      // now check for angle < 30°: in this case we swap with one of the edges the corner is part of
+      // now check for angle < 30 deg: in this case we swap with one of the edges the corner is part of
       for (int j=0; j<3; j++)
       {
         float fCosAngle = fCosAngles[j];