patch 8.0.0883: invalid memory access with nonsensical script

Problem:    Invalid memory access with nonsensical script.
Solution:   Check "dstlen" being positive. (Dominique Pelle)

Author: brammool

src/misc1.c

@@ -4180,13 +4180,18 @@ expand_env_esc(
 	    }
 	    else if ((src[0] == ' ' || src[0] == ',') && !one)
 		at_start = TRUE;
-	    *dst++ = *src++;
-	    --dstlen;
+	    if (dstlen > 0)
+	    {
+		*dst++ = *src++;
+		--dstlen;
 
-	    if (startstr != NULL && src - startstr_len >= srcp
-		    && STRNCMP(src - startstr_len, startstr, startstr_len) == 0)
-		at_start = TRUE;
+		if (startstr != NULL && src - startstr_len >= srcp
+			&& STRNCMP(src - startstr_len, startstr,
+							    startstr_len) == 0)
+		    at_start = TRUE;
+	    }
 	}
+
     }
     *dst = NUL;
 }

src/version.c

@@ -769,6 +769,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    883,
 /**/
     882,
 /**/