Merge pull request #7 from libgit2/ethomson/xmerge_malloc_zero

Don't try to malloc 0 bytes in xmerge

Author: ethomson

xmerge.c

@@ -709,19 +709,23 @@ int xdl_merge(mmfile_t *orig, mmfile_t *mf1, mmfile_t *mf2,
 		goto out;
 
 	if (!xscr1) {
-		result->ptr = xdl_malloc(mf2->size);
-		if (!result->ptr)
-			goto out;
+		if (mf2->size) {
+			result->ptr = xdl_malloc(mf2->size);
+			if (!result->ptr)
+				goto out;
+			memcpy(result->ptr, mf2->ptr, mf2->size);
+			result->size = mf2->size;
+		}
 		status = 0;
-		memcpy(result->ptr, mf2->ptr, mf2->size);
-		result->size = mf2->size;
 	} else if (!xscr2) {
-		result->ptr = xdl_malloc(mf1->size);
-		if (!result->ptr)
-			goto out;
+		if (mf1->size) {
+			result->ptr = xdl_malloc(mf1->size);
+			if (!result->ptr)
+				goto out;
+			memcpy(result->ptr, mf1->ptr, mf1->size);
+			result->size = mf1->size;
+		}
 		status = 0;
-		memcpy(result->ptr, mf1->ptr, mf1->size);
-		result->size = mf1->size;
 	} else {
 		status = xdl_do_merge(&xe1, xscr1,
 				      &xe2, xscr2,