diff -rauN icewm-1.3.8/src/wmapp.cc icewm-1.3.8-pixmap-null-ref-patch/src/wmapp.cc
--- icewm-1.3.8/src/wmapp.cc	2013-11-17 17:54:39.000000000 +0100
+++ icewm-1.3.8-pixmap-null-ref-patch/src/wmapp.cc	2018-06-06 21:30:29.778296503 +0200
@@ -621,14 +620,14 @@
 
         for (int a = 0; a <= 1; a++) {
             for (int b = 0; b <= 1; b++) {
-                frameT[a][b]->replicate(true, copyMask);
-                frameB[a][b]->replicate(true, copyMask);
-                frameL[a][b]->replicate(false, copyMask);
-                frameR[a][b]->replicate(false, copyMask);
+				if( frameT[a][b] != null ) frameT[a][b]->replicate(true, copyMask);
+                if( frameB[a][b] != null ) frameB[a][b]->replicate(true, copyMask);
+                if( frameL[a][b] != null ) frameL[a][b]->replicate(false, copyMask);
+                if( frameR[a][b] != null ) frameR[a][b]->replicate(false, copyMask);
             }
-            titleS[a]->replicate(true, copyMask);
-            titleT[a]->replicate(true, copyMask);
-            titleB[a]->replicate(true, copyMask);
+            if( titleS[a] != null ) titleS[a]->replicate(true, copyMask);
+            if( titleT[a] != null ) titleT[a]->replicate(true, copyMask);
+            if( titleB[a] != null ) titleB[a]->replicate(true, copyMask);
         }
 
         menuButton[0] = paths->loadPixmap(0, "menuButtonI.xpm");