patch 8.1.0989: various small code ugliness

Problem:    Various small code ugliness.
Solution:   Remove pointless NULL checks. Fix function calls. Fix typos.
            (Dominique Pelle, closes #4060)
diff --git a/src/os_win32.c b/src/os_win32.c
index 4ac5ebd..df6f7db 100644
--- a/src/os_win32.c
+++ b/src/os_win32.c
@@ -2646,7 +2646,7 @@
     if (cterm_normal_bg_color == 0)
 	cterm_normal_bg_color = ((g_attrCurrent >> 4) & 0xf) + 1;
 
-    // Fg and Bg color index nunmber at startup
+    // Fg and Bg color index number at startup
     g_color_index_fg = g_attrDefault & 0xf;
     g_color_index_bg = (g_attrDefault >> 4) & 0xf;
 
@@ -4210,8 +4210,7 @@
 	    (LPSTARTUPINFOW)si,	/* Startup information */
 	    pi);			/* Process information */
 	vim_free(wcmd);
-	if (wcwd != NULL)
-	    vim_free(wcwd);
+	vim_free(wcwd);
 	return ret;
     }
 fallback:
@@ -5312,8 +5311,8 @@
 			*((WCHAR*)gap->ga_data + gap->ga_len++) = wval[n];
 		    *((WCHAR*)gap->ga_data + gap->ga_len++) = L'\0';
 		}
-		if (wkey != NULL) vim_free(wkey);
-		if (wval != NULL) vim_free(wval);
+		vim_free(wkey);
+		vim_free(wval);
 	    }
 	}
     }