Cleanup: Solidify modifier: Remove unneccessary error message.

For any modifier, the expected output when the input mesh is empty, is an
empty mesh. So this error message was useless, and could spam the
console in some usecases of the modifier stack...

Reviewed By: weasel, mont29

Differential Revision: https://developer.blender.org/D7571

source/blender/modifiers/intern/MOD_solidify_extrude.c

@@ -1233,10 +1233,6 @@ Mesh *MOD_solidify_extrude_applyModifier(ModifierData *md,
     MEM_freeN(poly_nors);
   }
 
-  if (numPolys == 0 && numVerts != 0) {
-    modifier_setError(md, "Faces needed for useful output");
-  }
-
   return result;
 }
 

source/blender/modifiers/intern/MOD_solidify_nonmanifold.c

@@ -149,7 +149,6 @@ Mesh *MOD_solidify_nonmanifold_applyModifier(ModifierData *md,
   const uint numLoops = (uint)mesh->totloop;
 
   if (numPolys == 0 && numVerts != 0) {
-    modifier_setError(md, "Faces needed for useful output");
     return mesh;
   }